Thanks! I had to make a git stash but then it worked out.

Unrelated - is it “safe” to update Node.js and do a sudo apt update and sudo apt upgrade of the Rpi, or could I expect issues? Sorry for noob Qs

npm WARN npm npm does not support Node.js v10.23.1
npm WARN npm You should probably upgrade to a newer version of node as we
npm WARN npm can't make any promises that npm will work with this version.
npm WARN npm Supported releases of Node.js are the latest release of 4, 6, 7, 8, 9.
npm WARN npm You can find the latest version at https://nodejs.org/

cd ~/MagicMirror
rm .git/refs/tags/v2.13.0
rm .git/refs/tags/v2.14.0
then the purge refs command again

git remote prune origin

thx, I tried this

pi@raspberrypi:~/MagicMirror $ git remote prune origin
pi@raspberrypi:~/MagicMirror $ git pull && npm install
error: cannot lock ref 'refs/tags/v2.13.0': unable to resolve reference 'refs/tags/v2.13.0': reference broken
From https://github.com/MichMich/MagicMirror
 ! [new tag]           v2.13.0    -> v2.13.0  (unable to update local ref)
error: cannot lock ref 'refs/tags/v2.14.0': unable to resolve reference 'refs/tags/v2.14.0': reference broken
 ! [new tag]           v2.14.0    -> v2.14.0  (unable to update local ref)

git remote prune origin