Problem solved. It was the OpenTasks app.
SOLUTION: In the permissions settings of the OpenTasks app the option “Contacts” (in german “Kontakte”) has to be turned on.
Thanks for your help.
I installed Open Tasks from fdroid, and then DAVdroid. However, DAVdroid complains about the fact that Open Tasks isn’t installed. I uninstalled DAVdroid and reinstalled it again, and the problem remains. Did the same thing with Open Tasks, still the same thing.
Here’s my debug information:
Thanks for your work!
(Un)fortunately, this problem can’t be reproduced here. Please provide steps to reproduce, including when exactly which error message appears.
The steps are the following:
The OpenTasks app is not available, so DAVdroid won’t be able to synchronize task lists.
After installing OpenTasks, you have to RE-INSTALL DAVdroid and add your accounts again (Android bug)."
I can’t reproduce this on my devices. Maybe your firmware somehow doesn’t allow DAVdroid to list installed packages?
I see, interesting. The thing is I can’t install a custom ROM on my device, as there are none available.
Do you have an idea of a workaround?
Thanks for your help, and thanks again for your great work.
It seems it does work fine when device is rooted.