I did try Bazzite after this post - defaults to Nvidia 560 driver, which is still not the stable. Also installs extra things that I had to turn off - ended up re-wiping and going back to Fedora 40. I may retry in the future, though - but in general, I'm less interested in immutable at this point.
Thank you for the suggestions!
Yes, and thank you for your interest in helping. Appreciated! After an update, I will eventually reboot. When doing so, the options in the gear at the Gnome login will be
Both of these options are X11. I verify this with $ echo $XDG_SESSION_TYPE and see X11. When Wayland is working, the Gnome login will show four session types:
I haven't been able to locate a log file where something looks relevant to the decision made at boot for XDG, Wayland, or X11 that chooses one over the other. It's just as though Wayland stops being an option. 3 or 4 updates later, I'll have Wayland back again - but no idea why it comes and goes. My caveman intuition tells me it happens around nvidia updates, but I haven't kept strict notes on that.