the problem I'll be describing might be caused by different reasons:
on linux opensuse leap 15.1 gnome (wayland) I can share e.g. mupdf but not evince or libreoffice in chromium jitsi session with screen share application window
another participant on windows tried to share a pdf document using microsoft office 365 and it seemed to show on his browser, but not on the other conference participants' browsers (one chromium on linux as in 1., the other firefox on windows), so he could not share his screen
I could not find any information on this topic using search machines. So I would appreciate if there is any answer on this out there in the community.
Looking forward to solving this ...
Cheers
JFM
PS: on the setup described in 1. also obs studio fails to screencast, maybe there is something related to this system setup causing this problem, some video driver setting e.g.?
This is probably related to Wayland, which has more restrictions than classic Gnome. Since you are having the same issue with OBS this sounds like this a classic Wayland permission issue. I know they are working on implementing screen sharing support via pipewire but no idea how far this is.
You might try to switch back to Gnome on the X-Server until this is properly implemented.