Bufff, workarounded using:
QTWEBENGINE_DISABLE_SANDBOX=1 ./Slicer
I am guessing this is not he best solution though.
For debugging, using these flags helped:
QTWEBENGINE_CHROMIUM_FLAGS="--enable-logging --log-level=0 --v=1" ./Slicer
By the way, these are the warnings generated during loading:
Remote debugging server started successfully. Try pointing a Chromium-based browser to http://127.0.0.1:1337
"" 1 "JQuery not loaded - Failed to trigger webkitvisibilitychange"
"https://extensions.slicer.org/catalog/All/30746/linux" 0 "Mixed Content: The page at 'https://extensions.slicer.org/catalog/All/30746/linux' was loaded over HTTPS, but requested an insecure image 'http://www.example.com/Slicer/Extensions/BreastImplantAnalyzer.png'. This content should also be served over HTTPS."
Mixed Content: The page at 'https://extensions.slicer.org/catalog/All/30746/linux' was loaded over HTTPS, but requested an insecure image 'http://www.example.com/Slicer/Extensions/BreastImplantAnalyzer.png'. This content should also be served over HTTPS.
"https://extensions.slicer.org/catalog/All/30746/linux" 0 "Mixed Content: The page at 'https://extensions.slicer.org/catalog/All/30746/linux' was loaded over HTTPS, but requested an insecure image 'http://www.slicer.org/slicerWiki/images/b/bc/BaselineFollowupSCANRegisteredCMFreg2.png'. This content should also be served over HTTPS."
Mixed Content: The page at 'https://extensions.slicer.org/catalog/All/30746/linux' was loaded over HTTPS, but requested an insecure image 'http://www.slicer.org/slicerWiki/images/b/bc/BaselineFollowupSCANRegisteredCMFreg2.png'. This content should also be served over HTTPS.
"https://extensions.slicer.org/catalog/All/30746/linux" 0 "Mixed Content: The page at 'https://extensions.slicer.org/catalog/All/30746/linux' was loaded over HTTPS, but requested an insecure image 'http://wiki.slicer.org/slicerWiki/images/2/2a/CarreraSliceEffect.png'. This content should also be served over HTTPS."
Mixed Content: The page at 'https://extensions.slicer.org/catalog/All/30746/linux' was loaded over HTTPS, but requested an insecure image 'http://wiki.slicer.org/slicerWiki/images/2/2a/CarreraSliceEffect.png'. This content should also be served over HTTPS.
"https://extensions.slicer.org/catalog/All/30746/linux" 0 "Mixed Content: The page at 'https://extensions.slicer.org/catalog/All/30746/linux' was loaded over HTTPS, but requested an insecure image 'http://www.slicer.org/slicerWiki/images/b/b9/ChangeTracker_logo.png'. This content should also be served over HTTPS."
Mixed Content: The page at 'https://extensions.slicer.org/catalog/All/30746/linux' was loaded over HTTPS, but requested an insecure image 'http://www.slicer.org/slicerWiki/images/b/b9/ChangeTracker_logo.png'. This content should also be served over HTTPS.
"https://extensions.slicer.org/catalog/All/30746/linux" 0 "Mixed Content: The page at 'https://extensions.slicer.org/catalog/All/30746/linux' was loaded over HTTPS, but requested an insecure image 'http://www.example.com/Slicer/Extensions/CleverSeg.png'. This content should also be served over HTTPS."
Mixed Content: The page at 'https://extensions.slicer.org/catalog/All/30746/linux' was loaded over HTTPS, but requested an insecure image 'http://www.example.com/Slicer/Extensions/CleverSeg.png'. This content should also be served over HTTPS.
"https://extensions.slicer.org/catalog/All/30746/linux" 0 "Mixed Content: The page at 'https://extensions.slicer.org/catalog/All/30746/linux' was loaded over HTTPS, but requested an insecure image 'http://www.slicer.org/slicerWiki/images/e/e1/CornerAnnotationIcon.png'. This content should also be served over HTTPS."
Mixed Content: The page at 'https://extensions.slicer.org/catalog/All/30746/linux' was loaded over HTTPS, but requested an insecure image 'http://www.slicer.org/slicerWiki/images/e/e1/CornerAnnotationIcon.png'. This content should also be served over HTTPS.
"https://extensions.slicer.org/catalog/All/30746/linux" 0 "Mixed Content: The page at 'https://extensions.slicer.org/catalog/All/30746/linux' was loaded over HTTPS, but requested an insecure image 'http://www.slicer.org/slicerWiki/images/b/b7/CurveMakerIcon.png'. This content should also be served over HTTPS."
Mixed Content: The page at 'https://extensions.slicer.org/catalog/All/30746/linux' was loaded over HTTPS, but requested an insecure image 'http://www.slicer.org/slicerWiki/images/b/b7/CurveMakerIcon.png'. This content should also be served over HTTPS.
"https://extensions.slicer.org/catalog/All/30746/linux" 0 "Mixed Content: The page at 'https://extensions.slicer.org/catalog/All/30746/linux' was loaded over HTTPS, but requested an insecure image 'http://slicer.org/slicerWiki/images/9/92/DSC_logo_Resized.png'. This content should also be served over HTTPS."
Mixed Content: The page at 'https://extensions.slicer.org/catalog/All/30746/linux' was loaded over HTTPS, but requested an insecure image 'http://slicer.org/slicerWiki/images/9/92/DSC_logo_Resized.png'. This content should also be served over HTTPS.
"https://extensions.slicer.org/catalog/All/30746/linux" 0 "Mixed Content: The page at 'https://extensions.slicer.org/catalog/All/30746/linux' was loaded over HTTPS, but requested an insecure image 'http://www.slicer.org/slicerWiki/images/a/ac/ErodeDilateLabelIcon.png'. This content should also be served over HTTPS."
Mixed Content: The page at 'https://extensions.slicer.org/catalog/All/30746/linux' was loaded over HTTPS, but requested an insecure image 'http://www.slicer.org/slicerWiki/images/a/ac/ErodeDilateLabelIcon.png'. This content should also be served over HTTPS.
"https://extensions.slicer.org/catalog/All/30746/linux" 0 "Mixed Content: The page at 'https://extensions.slicer.org/catalog/All/30746/linux' was loaded over HTTPS, but requested an insecure image 'http://www.slicer.org/slicerWiki/images/1/16/FilmDosimetry_Logo_128x128.png'. This content should also be served over HTTPS."
Mixed Content: The page at 'https://extensions.slicer.org/catalog/All/30746/linux' was loaded over HTTPS, but requested an insecure image 'http://www.slicer.org/slicerWiki/images/1/16/FilmDosimetry_Logo_128x128.png'. This content should also be served over HTTPS.
"https://extensions.slicer.org/catalog/All/30746/linux" 0 "Mixed Content: The page at 'https://extensions.slicer.org/catalog/All/30746/linux' was loaded over HTTPS, but requested an insecure image 'http://www.slicer.org/slicerWiki/images/f/f1/GelDosimetry_Logo_128x128.png'. This content should also be served over HTTPS."
Mixed Content: The page at 'https://extensions.slicer.org/catalog/All/30746/linux' was loaded over HTTPS, but requested an insecure image 'http://www.slicer.org/slicerWiki/images/f/f1/GelDosimetry_Logo_128x128.png'. This content should also be served over HTTPS.
"https://extensions.slicer.org/catalog/All/30746/linux" 0 "Mixed Content: The page at 'https://extensions.slicer.org/catalog/All/30746/linux' was loaded over HTTPS, but requested an insecure image 'http://www.slicer.org/slicerWiki/images/a/a7/GyroGuide.png'. This content should also be served over HTTPS."
Mixed Content: The page at 'https://extensions.slicer.org/catalog/All/30746/linux' was loaded over HTTPS, but requested an insecure image 'http://www.slicer.org/slicerWiki/images/a/a7/GyroGuide.png'. This content should also be served over HTTPS.
"https://extensions.slicer.org/catalog/All/30746/linux" 0 "Mixed Content: The page at 'https://extensions.slicer.org/catalog/All/30746/linux' was loaded over HTTPS, but requested an insecure image 'http://www.slicer.org/slicerWiki/images/e/e5/QuickToolsLogo.png'. This content should also be served over HTTPS."
Mixed Content: The page at 'https://extensions.slicer.org/catalog/All/30746/linux' was loaded over HTTPS, but requested an insecure image 'http://www.slicer.org/slicerWiki/images/e/e5/QuickToolsLogo.png'. This content should also be served over HTTPS.
"https://extensions.slicer.org/catalog/All/30746/linux" 0 "Mixed Content: The page at 'https://extensions.slicer.org/catalog/All/30746/linux' was loaded over HTTPS, but requested an insecure image 'http://www.slicer.org/slicerWiki/images/e/e8/MatlabBridgeLogo.png'. This content should also be served over HTTPS."
Mixed Content: The page at 'https://extensions.slicer.org/catalog/All/30746/linux' was loaded over HTTPS, but requested an insecure image 'http://www.slicer.org/slicerWiki/images/e/e8/MatlabBridgeLogo.png'. This content should also be served over HTTPS.
"https://extensions.slicer.org/catalog/All/30746/linux" 0 "Mixed Content: The page at 'https://extensions.slicer.org/catalog/All/30746/linux' was loaded over HTTPS, but requested an insecure image 'http://www.slicer.org/slicerWiki/index.php/File:ModelClipIcon.png'. This content should also be served over HTTPS."
Mixed Content: The page at 'https://extensions.slicer.org/catalog/All/30746/linux' was loaded over HTTPS, but requested an insecure image 'http://www.slicer.org/slicerWiki/index.php/File:ModelClipIcon.png'. This content should also be served over HTTPS.
"https://extensions.slicer.org/catalog/All/30746/linux" 0 "Mixed Content: The page at 'https://extensions.slicer.org/catalog/All/30746/linux' was loaded over HTTPS, but requested an insecure image 'http://slicer.org/slicerWiki/images/4/43/Slicer4ExtensionModelToModelDistance.png'. This content should also be served over HTTPS."
Mixed Content: The page at 'https://extensions.slicer.org/catalog/All/30746/linux' was loaded over HTTPS, but requested an insecure image 'http://slicer.org/slicerWiki/images/4/43/Slicer4ExtensionModelToModelDistance.png'. This content should also be served over HTTPS.
"https://extensions.slicer.org/catalog/All/30746/linux" 0 "Mixed Content: The page at 'https://extensions.slicer.org/catalog/All/30746/linux' was loaded over HTTPS, but requested an insecure image 'http://www.slicer.org/slicerWiki/images/2/2e/OpenCAD.PNG'. This content should also be served over HTTPS."
Mixed Content: The page at 'https://extensions.slicer.org/catalog/All/30746/linux' was loaded over HTTPS, but requested an insecure image 'http://www.slicer.org/slicerWiki/images/2/2e/OpenCAD.PNG'. This content should also be served over HTTPS.
"https://extensions.slicer.org/catalog/All/30746/linux" 0 "Mixed Content: The page at 'https://extensions.slicer.org/catalog/All/30746/linux' was loaded over HTTPS, but requested an insecure image 'http://www.slicer.org/slicerWiki/images/a/ac/PAAlogo-small.png'. This content should also be served over HTTPS."
Mixed Content: The page at 'https://extensions.slicer.org/catalog/All/30746/linux' was loaded over HTTPS, but requested an insecure image 'http://www.slicer.org/slicerWiki/images/a/ac/PAAlogo-small.png'. This content should also be served over HTTPS.
"https://extensions.slicer.org/catalog/All/30746/linux" 0 "Mixed Content: The page at 'https://extensions.slicer.org/catalog/All/30746/linux' was loaded over HTTPS, but requested an insecure image 'http://www.slicer.org/slicerWiki/images/2/21/PerkTutorLogo.png'. This content should also be served over HTTPS."
Mixed Content: The page at 'https://extensions.slicer.org/catalog/All/30746/linux' was loaded over HTTPS, but requested an insecure image 'http://www.slicer.org/slicerWiki/images/2/21/PerkTutorLogo.png'. This content should also be served over HTTPS.
"https://extensions.slicer.org/catalog/All/30746/linux" 0 "Mixed Content: The page at 'https://extensions.slicer.org/catalog/All/30746/linux' was loaded over HTTPS, but requested an insecure image 'http://www.slicer.org/slicerWiki/images/b/b1/DPetBrainQuantification.png'. This content should also be served over HTTPS."
Mixed Content: The page at 'https://extensions.slicer.org/catalog/All/30746/linux' was loaded over HTTPS, but requested an insecure image 'http://www.slicer.org/slicerWiki/images/b/b1/DPetBrainQuantification.png'. This content should also be served over HTTPS.
"https://extensions.slicer.org/catalog/All/30746/linux" 0 "Mixed Content: The page at 'https://extensions.slicer.org/catalog/All/30746/linux' was loaded over HTTPS, but requested an insecure image 'http://www.slicer.org/slicerWiki/images/a/a7/Portplacement_icon.png'. This content should also be served over HTTPS."
Mixed Content: The page at 'https://extensions.slicer.org/catalog/All/30746/linux' was loaded over HTTPS, but requested an insecure image 'http://www.slicer.org/slicerWiki/images/a/a7/Portplacement_icon.png'. This content should also be served over HTTPS.
"https://extensions.slicer.org/catalog/All/30746/linux" 0 "Mixed Content: The page at 'https://extensions.slicer.org/catalog/All/30746/linux' was loaded over HTTPS, but requested an insecure image 'http://wiki.slicer.org/slicerWiki/images/d/d6/ResectionPlannerLogo.png'. This content should also be served over HTTPS."
Mixed Content: The page at 'https://extensions.slicer.org/catalog/All/30746/linux' was loaded over HTTPS, but requested an insecure image 'http://wiki.slicer.org/slicerWiki/images/d/d6/ResectionPlannerLogo.png'. This content should also be served over HTTPS.
"https://extensions.slicer.org/catalog/All/30746/linux" 0 "Mixed Content: The page at 'https://extensions.slicer.org/catalog/All/30746/linux' was loaded over HTTPS, but requested an insecure image 'http://viewvc.slicer.org/viewvc.cgi/Slicer4/trunk/Extensions/Testing/SNRMeasurement/SNRMeasurement.png?revision=21745&view=co'. This content should also be served over HTTPS."
Mixed Content: The page at 'https://extensions.slicer.org/catalog/All/30746/linux' was loaded over HTTPS, but requested an insecure image 'http://viewvc.slicer.org/viewvc.cgi/Slicer4/trunk/Extensions/Testing/SNRMeasurement/SNRMeasurement.png?revision=21745&view=co'. This content should also be served over HTTPS.
"https://extensions.slicer.org/catalog/All/30746/linux" 0 "Mixed Content: The page at 'https://extensions.slicer.org/catalog/All/30746/linux' was loaded over HTTPS, but requested an insecure image 'http://www.na-mic.org/Wiki/images/a/ad/Spharm-pdm-icon.png'. This content should also be served over HTTPS."
Mixed Content: The page at 'https://extensions.slicer.org/catalog/All/30746/linux' was loaded over HTTPS, but requested an insecure image 'http://www.na-mic.org/Wiki/images/a/ad/Spharm-pdm-icon.png'. This content should also be served over HTTPS.
"https://extensions.slicer.org/catalog/All/30746/linux" 0 "Mixed Content: The page at 'https://extensions.slicer.org/catalog/All/30746/linux' was loaded over HTTPS, but requested an insecure image 'http://www.slicer.org/slicerWiki/images/b/ba/SegAidedRegSquareFocus128.png'. This content should also be served over HTTPS."
Mixed Content: The page at 'https://extensions.slicer.org/catalog/All/30746/linux' was loaded over HTTPS, but requested an insecure image 'http://www.slicer.org/slicerWiki/images/b/ba/SegAidedRegSquareFocus128.png'. This content should also be served over HTTPS.
"https://extensions.slicer.org/catalog/All/30746/linux" 0 "Mixed Content: The page at 'https://extensions.slicer.org/catalog/All/30746/linux' was loaded over HTTPS, but requested an insecure image 'http://www.slicer.org/slicerWiki/images/f/f2/SkullStripper.png'. This content should also be served over HTTPS."
Mixed Content: The page at 'https://extensions.slicer.org/catalog/All/30746/linux' was loaded over HTTPS, but requested an insecure image 'http://www.slicer.org/slicerWiki/images/f/f2/SkullStripper.png'. This content should also be served over HTTPS.
"https://extensions.slicer.org/catalog/All/30746/linux" 0 "Mixed Content: The page at 'https://extensions.slicer.org/catalog/All/30746/linux' was loaded over HTTPS, but requested an insecure image 'http://raw.githubusercontent.com/SlicerDMRI/slicerdmri.github.io/master/images/DMRI_3D_SLICER-icon.png'. This content should also be served over HTTPS."
Mixed Content: The page at 'https://extensions.slicer.org/catalog/All/30746/linux' was loaded over HTTPS, but requested an insecure image 'http://raw.githubusercontent.com/SlicerDMRI/slicerdmri.github.io/master/images/DMRI_3D_SLICER-icon.png'. This content should also be served over HTTPS.
"https://extensions.slicer.org/catalog/All/30746/linux" 0 "Mixed Content: The page at 'https://extensions.slicer.org/catalog/All/30746/linux' was loaded over HTTPS, but requested an insecure image 'http://raw.githubusercontent.com/QIICR/SlicerDevelopmentToolbox/master/Resources/Icons/SlicerDevelopmentToolbox.png'. This content should also be served over HTTPS."
Mixed Content: The page at 'https://extensions.slicer.org/catalog/All/30746/linux' was loaded over HTTPS, but requested an insecure image 'http://raw.githubusercontent.com/QIICR/SlicerDevelopmentToolbox/master/Resources/Icons/SlicerDevelopmentToolbox.png'. This content should also be served over HTTPS.
"https://extensions.slicer.org/catalog/All/30746/linux" 0 "Mixed Content: The page at 'https://extensions.slicer.org/catalog/All/30746/linux' was loaded over HTTPS, but requested an insecure image 'http://www.slicer.org/slicerWiki/images/f/ff/SlicerHeart_Logo_128x128.png'. This content should also be served over HTTPS."
Mixed Content: The page at 'https://extensions.slicer.org/catalog/All/30746/linux' was loaded over HTTPS, but requested an insecure image 'http://www.slicer.org/slicerWiki/images/f/ff/SlicerHeart_Logo_128x128.png'. This content should also be served over HTTPS.
"https://extensions.slicer.org/catalog/All/30746/linux" 0 "Mixed Content: The page at 'https://extensions.slicer.org/catalog/All/30746/linux' was loaded over HTTPS, but requested an insecure image 'http://www.slicer.org/slicerWiki/images/2/2b/SlicerIGTLogo.png'. This content should also be served over HTTPS."
Mixed Content: The page at 'https://extensions.slicer.org/catalog/All/30746/linux' was loaded over HTTPS, but requested an insecure image 'http://www.slicer.org/slicerWiki/images/2/2b/SlicerIGTLogo.png'. This content should also be served over HTTPS.
"https://extensions.slicer.org/catalog/All/30746/linux" 0 "Mixed Content: The page at 'https://extensions.slicer.org/catalog/All/30746/linux' was loaded over HTTPS, but requested an insecure image 'http://wiki.slicer.org/slicerWiki/images/8/87/SlicerProstate_Logo_1.0_128x128.png'. This content should also be served over HTTPS."
Mixed Content: The page at 'https://extensions.slicer.org/catalog/All/30746/linux' was loaded over HTTPS, but requested an insecure image 'http://wiki.slicer.org/slicerWiki/images/8/87/SlicerProstate_Logo_1.0_128x128.png'. This content should also be served over HTTPS.
"https://extensions.slicer.org/catalog/All/30746/linux" 0 "Mixed Content: The page at 'https://extensions.slicer.org/catalog/All/30746/linux' was loaded over HTTPS, but requested an insecure image 'http://www.slicer.org/slicerWiki/images/2/29/SlicerRT_Logo_3.0_128x128.png'. This content should also be served over HTTPS."
Mixed Content: The page at 'https://extensions.slicer.org/catalog/All/30746/linux' was loaded over HTTPS, but requested an insecure image 'http://www.slicer.org/slicerWiki/images/2/29/SlicerRT_Logo_3.0_128x128.png'. This content should also be served over HTTPS.
"https://extensions.slicer.org/catalog/All/30746/linux" 0 "Mixed Content: The page at 'https://extensions.slicer.org/catalog/All/30746/linux' was loaded over HTTPS, but requested an insecure image 'http://www.slicer.org/slicerWiki/images/6/64/SlicerToKiwiExporterLogo.png'. This content should also be served over HTTPS."
Mixed Content: The page at 'https://extensions.slicer.org/catalog/All/30746/linux' was loaded over HTTPS, but requested an insecure image 'http://www.slicer.org/slicerWiki/images/6/64/SlicerToKiwiExporterLogo.png'. This content should also be served over HTTPS.
"https://extensions.slicer.org/catalog/All/30746/linux" 0 "Mixed Content: The page at 'https://extensions.slicer.org/catalog/All/30746/linux' was loaded over HTTPS, but requested an insecure image 'http://www.nitrc.org/project/screenshot.php?group_id=196&screenshot_id=269'. This content should also be served over HTTPS."
Mixed Content: The page at 'https://extensions.slicer.org/catalog/All/30746/linux' was loaded over HTTPS, but requested an insecure image 'http://www.nitrc.org/project/screenshot.php?group_id=196&screenshot_id=269'. This content should also be served over HTTPS.
"https://extensions.slicer.org/catalog/All/30746/linux" 0 "Mixed Content: The page at 'https://extensions.slicer.org/catalog/All/30746/linux' was loaded over HTTPS, but requested an insecure image 'http://www.slicer.org/slicerWiki/images/c/cd/SwissSkullStripper.png'. This content should also be served over HTTPS."
Mixed Content: The page at 'https://extensions.slicer.org/catalog/All/30746/linux' was loaded over HTTPS, but requested an insecure image 'http://www.slicer.org/slicerWiki/images/c/cd/SwissSkullStripper.png'. This content should also be served over HTTPS.
"https://extensions.slicer.org/catalog/All/30746/linux" 0 "Mixed Content: The page at 'https://extensions.slicer.org/catalog/All/30746/linux' was loaded over HTTPS, but requested an insecure image 'http://slicer.org/slicerWiki/images/3/32/T1_Mapping_Logo_Resized.png'. This content should also be served over HTTPS."
Mixed Content: The page at 'https://extensions.slicer.org/catalog/All/30746/linux' was loaded over HTTPS, but requested an insecure image 'http://slicer.org/slicerWiki/images/3/32/T1_Mapping_Logo_Resized.png'. This content should also be served over HTTPS.
"https://extensions.slicer.org/catalog/All/30746/linux" 0 "Mixed Content: The page at 'https://extensions.slicer.org/catalog/All/30746/linux' was loaded over HTTPS, but requested an insecure image 'http://wiki.slicer.org/slicerWiki/images/9/92/TCIABrowser_logo.png'. This content should also be served over HTTPS."
Mixed Content: The page at 'https://extensions.slicer.org/catalog/All/30746/linux' was loaded over HTTPS, but requested an insecure image 'http://wiki.slicer.org/slicerWiki/images/9/92/TCIABrowser_logo.png'. This content should also be served over HTTPS.
"https://extensions.slicer.org/catalog/All/30746/linux" 0 "Mixed Content: The page at 'https://extensions.slicer.org/catalog/All/30746/linux' was loaded over HTTPS, but requested an insecure image 'http://www.slicer.org/slicerWiki/images/c/c2/VolumeClipLogo.png'. This content should also be served over HTTPS."
Mixed Content: The page at 'https://extensions.slicer.org/catalog/All/30746/linux' was loaded over HTTPS, but requested an insecure image 'http://www.slicer.org/slicerWiki/images/c/c2/VolumeClipLogo.png'. This content should also be served over HTTPS.
"https://extensions.slicer.org/catalog/All/30746/linux" 0 "A cookie associated with a cross-site resource at http://www.nitrc.org/ was set without the `SameSite` attribute. A future release of Chrome will only deliver cookies with cross-site requests if they are set with `SameSite=None` and `Secure`. You can review cookies in developer tools under Application>Storage>Cookies and see more details at https://www.chromestatus.com/feature/5088147346030592 and https://www.chromestatus.com/feature/5633521622188032."
A cookie associated with a cross-site resource at http://www.nitrc.org/ was set without the `SameSite` attribute. A future release of Chrome will only deliver cookies with cross-site requests if they are set with `SameSite=None` and `Secure`. You can review cookies in developer tools under Application>Storage>Cookies and see more details at https://www.chromestatus.com/feature/5088147346030592 and https://www.chromestatus.com/feature/5633521622188032.