Hi, I’m on Linux mint 21, and I am using Slicer 5.6.1.
I cannot see a 3D view, even after pressing the center view button.
The 3D view is in the top right corner. It seems to be working. Do you have some kind of data in the scene that is supposed to show up there but doesn’t? The question is not very clear, and the screenshot does not show the scene content.
To display data in the 3D view, you could for example enable volume rendering of the corresponding dataset.