Printed pages are blank if sidebar is not hidden
This seems to happen on all flavors of GitLab (at least gitlab.com and Omnibus).
When printing any page with the left sidebar visible, all pages of the document are blank. Of course the left sidebar is always hidden in the print layout, but for some reason the state of the sidebar in the active screen layout seems to affect the printed document ...
When printing to PDF, the document actually contains selectable text, but it seems to be white on white. The content can also be revealed by enabling the "Background graphics" option in the print dialogue, but this adds a grey background behind the content (see screenshot below).
Once the sidebar is hidden via the button or through reducing window width, the printed content becomes visible again.
The issue is reproducibe in Windows on Chrome and Edge (120.0). In Firefox (121.0) is seems to happen on some machines, but works on others.