I finally successfully upgraded to 42. As the offline upgrade from 40 to 41 also didn’t work, I tried it with
sudo dnf upgrade --releasever=41 --allowerasing -y
This worked like a charm and after a reboot my system was fully working with Fedora 41. Using dnf5 I tried to follow the steps in Upgrading Fedora Linux Using DNF System Plugin :: Fedora Docs. However the
sudo dnf5 offline reboot
again lead to an instant reboot into Fedora 41. However, this time I had logs.
Error reading the package header from file ...
With the help of google I realize I ran into a similar issue as in Dnf system-upgrade can fail on Raspberry Pi. Enabling systemd-timesyncd, which I hadn’t before and then trying the offline upgrade again (with dnf5 offline reboot) it worked like a charm. Thank you to @theprogram and @tqcharm for helping me with this issue.