@sdetweil
I did (read my way through all the posts)
HOWEVER,
https://forum.magicmirror.builders/topic/10859/new-update-upgrade-script-ready-for-testing/2
told me to run
bash -c "$(curl -sL https://raw.githubusercontent.com/sdetweil/MagicMirror_scripts/master/raspberry.sh)"
and that made me a new installation that did work.
Sometimes you have to sledgehammer things, I guess.
Thanks for offering to help,
karl