I don’t know exactly. after a lot of error messages appeared and openhab no longer started, I used the backup SD again.
I suspect it is due to the expired repo key:
https://community.openhab.org/t/linux-repo-public-key-is-expiring-soon/147905
I read that later.
I’m currently making a new backup and will try again.
My Guide is here:
https://www.raspberrypi.com/documentation/computers/os.html#upgrading-from-previous-operating-system-versions
It sounds easy:
sudo apt update
sudo apt full-upgrade
and hope that the oh-config is still running and that I can start the update there
Or do you have a better suggestion?