I logged in this morning to see the updater telling me that a partial upgrade was available, which I thought unusual as that’s usually for the xx04 or xx10 version changeovers. Hit “OK” and it started, then popped up a huge error box across the screen telling me I had no desktop installed (none of ubuntu-desktop
or many others, not recorded). Gnome then exited, back to a console login. Manually installed ubuntu-desktop
which pulled in a whole bunch of packages that I’d seen removed. Unable to restart the GUI, although I didn’t try too hard. Rebooted the PC and back to normal with the Gnome GUI.
Maybe one day in the future OS upgrades will work without making catastrophic stuff-ups along the way