After some frustration (nothing major, just little niggles), I am back with the mothership. I backed up my /home, re-partitioned the disc, installed Debian trixie to replace Ubuntu, and restored /home into its own partition [*]. I feel much more in control for some reason and there's little cruft in comparison.
Now spending an hour or two installing all the little utilities that I always forget I use and which are not installed by default, like davmail, kdeconnect, keynav, notmuch, rcs, ... but *Emacs* first of all, built from source, as it's my window manager!
[*] the Ubuntu installation by Dell on their workstations is all on one partition (/, /home, ...) which is rather annoying.