So, I updated Tumbleweed, and the updates to KDE caused my Plasma/Wayland session to restart, breaking the updates part way through. I wasn’t watching at the time so took some while to debug!
Spent some time learning how to use nm-cli, because new half-upgraded KDE wouldn’t load the network widget. It looks like something else may have changed and mucked up in the half-update (and of course I rebooted like a wise-man/dummy/i-dont-know-but-at-least-it-didnt-make-it-work) but iterations of trying things in nmcli eventually worked!
Finally tried zypper dup again and saw the session restart, so finished the job from the virtual terminal! At last, I seem to have a working computer again, and I might just brave updating my main laptop. (I cancelled the update while it was still downloading packages, after seeing the breakage on the other laptop!)
Further to this, my sound stopped working. “No input/output devices detected.”
Turned out if I went to the settings and turned on “show inactive devices”, then changed the Profile from ‘none’ to ‘Analog Stereo Duplex’, it went back to normal and worked. sigh
That’s what I get for a rolling release, I guess. I just hope the friends I set up on Linux Mint don’t get similar issues, since I’m not around to help when things break.