Update: I just redid the OS-update and now everything works fine. I guess there was some disturbance due to my attempts of restoring backup-data.
How to change account name?
Is there a way to change the name of a DavDroid account?
No. It’s impossible to rename accounts with Android <5.0, and for 5.0+ devices, it has not been implemented in DAVdroid (yet).
You can just delete the account and create a new one, which shouldn’t be that complicated.
Seems like it would be possible to rename the account on Android 5.0+, but existing local contacts/events can’t be moved.
At least the calendar provider prevents changing
Events.account_name(only the provider itself may change it, and the provider doesn’t have a rename method).
Renaming accounts has been implemented (with some cuts) and will be available in the next DAVdroid version.