This time my experiments worked, along the lines of
unset pool
delete the ix-applications dataset
reboot
set pool
I then did # watch -d k3s kubectl get pod -A
until I saw
and also
at which point I was satisfied that the problem was solved, inasmuch as I can now reinstall the apps (four out of the five will take a few tens of minutes, the last one I can’t remember how I first did it a couple of years ago and I’ve not needed to touch it since !).
It’s true that I may perhaps have made things worse along the way, but I did want to make progress now, whilst I had the opportunity, so I did my best by following various posts here and elsewhere.