I'll make a GNOME VM and grab the setting location if somebody here doesn't post it in a few hours, I had the same issue a few months ago. GNOME is weird. Gotta think like a Mac user to figure it out.
Thanks, John. Let me know if you find anything. I did find this https://help.gnome.org/admin/system-admin-guide/stable/logout-automatic.html..., which I will also check. The thing is, I would expect auto-logout to actually log me out. In other words, after a period of inactivity, I would expect that the login screen will appear. What I am seeing is different--the content of the screen continues to update (as if it was not logged out) but as soon as I move the mouse, it logs me out and I see the login screen again.