Mutter is not just a binary, but is also the library which provides ALL the graphics for the login screen and gnome-shell. So yes Ubuntu does use mutter for everything :)
If your Wayland login option has gone missing then that means the Wayland backend ("eglnative") of mutter had crashed during startup and so has been disabled. Please log a NEW bug for that by running:
Phillip,
Mutter is not just a binary, but is also the library which provides ALL the graphics for the login screen and gnome-shell. So yes Ubuntu does use mutter for everything :)
If your Wayland login option has gone missing then that means the Wayland backend ("eglnative") of mutter had crashed during startup and so has been disabled. Please log a NEW bug for that by running:
ubuntu-bug gnome-shell
on the machine.