Maybe it is just magic but it looks like to work so far.
Just try by yourself to find corner cases.
I will add comments here if/when I find issues with this configuration.
DAVdroid is asking for permission to sync tasks with OpenTasks. When I hit the button, nothing happens. I already tried to reinstall both apps (first OpenTasks, then DAVdroid), but nothing helps. Granting access to my system calendars and contacts is working fine. Both apps been running completely fine until Friday (10/14/2016). It is possible that my phone did an automated update of one of the apps in the background. I am not aware of this. I am using a Sony Xperia Z3 (D6603) with Android 6.0.1.
Please help me ASAP.
This happens when you click “deny” + “never ask again” in the Android dialog. You can go to Android settings / Apps / DAVdroid / Permissions and enable OpenTasks permissions there.
Thanks for your quick response. But I never denied this permission. And I also can’t find it in that settings.
@Roland It must be there, because Android 6 has dynamic permissions. It may be that Sony moved the setting to another place (and maybe “denys + never asks again” by default for you), but it must be somewhere.
@Roland I had the same problem, a reboot of the phone helped.
Additionally, I set the option to distrust any certificate and upon a manual sync, I was asked about the certificated and then again for the OpenTasks permission.