Since it seems that Ubuntu is going to stick with X for the upcoming 5 years, I think that this thread could be used to track the state of Wayland vs X.
*With GNOME 3.34 a big improvement DID already happen: You can start graphical apps with root privileges again. E.g. “sudo synaptic” and “sudo gedit” work again.
*Patches for Wayland fullscreen compositing bypass for games are on the way for GNOME 3.36, maybe even to some 3.34 point release: https://www.phoronix.com/scan.php?page=news_item&px=GNOME-PR-Pending-FS-Unredir
*Hans de Goede is finishing some patches to have a solid Xwayland resolution switching support. Especially WINE will benefit from that. That will be in 3.36 or even in some 3.34 point release.
*The GNOME VNC server Vino was deprecated and removed today upstream. Its replacement will be gnome-remote-desktop for both Wayland and X: https://gitlab.gnome.org/GNOME/gnome-build-meta/issues/92
Ubuntu doesn’t even ship Mutter with g-r-d support up to this day because the Security Team couldn’t find time to “MIR” that package yet.
*Firefox 69 is working flawlessly for me in Wayland mode. I expect that it will switch to automatic mode in Firefox 71or 72.