I’m a little confused, but I think the challenge is the buggy info overlay thing, not the OS. for me, Command J brings up the view options dialog in both library and develop, and it works fine in normal or full screen. The I (no modifier) key shows the info overlay, and if it isn’t showing it’s because it’s temporarily broken.
To fix it, I always flip from library to develop, trying to get it to show up, and cycling through the 3 options. I think once it is “working” it seems pretty good until you quit Lightroom.
There’s probably some “exact” sequence that will bring it back to normal when it doesn’t seem to work, but usually can get it working pretty quickly.
I’d try switching to normal screen mode until the overlay works, then I think it will work once you pop back to full screen.
I just tried it and the info overlay is working fine in full screen ....