Just some more info.
I downloaded the script update-debian-img.sh and executed with sudo.
I get the question if I want /etc/default/u-boot from the repo, or keep the existing one.
When I choose get the one from the repo, I end up in the same situation. When I choose keep the existing one, I can reboot after the upgrade. I see I have kernel 6.12.5. But everything feels slow.
Can someone with the new image share the contents of /etc/default/u-boot?
During the upgrade I also get questions about a post-login script and one other script. I chose no, but I’m also going to try with yes.
I’ll keep you posted about the progress.
Update: I was able to do a manual upgrade with the script update-debian-img.sh.
I followed the instructions in the picture update-from-bookworm.png.
After that I executed:
sudo apt update
sudo apt dist-upgrade
After a reboot the system was very slow, gnome-shell was consuming a lot of CPU.