It seems that your system has some problem with the MIT-SHM (MIT Shared Memory Extension) X11 extension. You may need to disable this X11 extensions to use Qt applications, such as Slicer. See for example this page for details.
Let us know if this launches Slicer correctly on your system:
# export QT_X11_NO_MITSHM=1
# export QT_DEBUG_PLUGINS=1
[root@fchredhattst01 Slicer-5.6.2-linux-amd64]# ls
bin include lib libexec resources share Slicer
[root@fchredhattst01 Slicer-5.6.2-linux-amd64]# ./Slicer
QFactoryLoader::QFactoryLoader() ignoring "com.trolltech.Qt.QInputContextFactoryInterface" since plugins are disabled in static builds
QFactoryLoader::QFactoryLoader() ignoring "com.trolltech.Qt.QStyleFactoryInterface" since plugins are disabled in static builds
QFactoryLoader::QFactoryLoader() ignoring "com.trolltech.Qt.QImageIOHandlerFactoryInterface" since plugins are disabled in static builds
/usr/local/Slicer-5.6.2-linux-amd64/bin/SlicerApp-real: symbol lookup error: /lib64/libk5crypto.so.3: undefined symbol: EVP_KDF_ctrl, version OPENSSL_1_1_1b