Yes, I installed davdroid from F-Droid and always upgraded it that way.
In that case, what if you uninstall the current app using Android’s
Settings / Apps menu and after that try installing the new version
I’m trying to avoid that because I will have to reconfigure my accounts,
which is quite annoying.
If you get the same error in F-Droid, download the APK and try
installing it manually. That will provide more information about
what’s going wrong.
Before I tried that, I remember I got a warning about shortage on space
some days ago, so even when I had more than 400MB of free space, I made
some more room and now I could upgrade without errors. For some reason
it seems like F-Droid needs a lot of temporary space? 😕
Anyway, thanks for the help and sorry for the noise!