Ok, I did a TCP dump of my testcase today with this pull request from @jochen314. I know it’s against 8.0 and not 8.1 but a rebase should not be too hard.
Now to the dump: The problem I see (I don’t know DAV very well unfortunately), is that DAVdroid only requests the
current-user-principal in the first request, but does not continue to query the
/ANONYMIZED_SHARED_FOLDER/ with a correct
PROPFIND in the next message.
A colleague tested our radicale server setup with his CalDAV Sync and CardDAV Sync and everything worked perfectly for him.
I hope this information/dump helps to finally fix #439 and also #249. If you need more info, let me know.