Then the issue is only, that for the first sync the ics that DAVx sends to SOGo does not contain METHOD:REPLY (and in consequence on organizer side the attendee status is not updated). But this METHOD:REPLY is set when I accept/decline the invitation after the initial sync was done.
Would it make sense to set METHOD:REPLY for the initial sync already if the organizer is not the attendee for that the invitation was accepted/declined?
DAVx⁵ never sets METHOD, because this is CalDAV Scheduling, which is not supported by DAVx⁵. The Android calendar provider doesn’t have the possibility to store the required fields for that.
But this METHOD:REPLY is set when I accept/decline the invitation after the initial sync was done.
I don’t understand that. Do you think DAVx⁵ sets METHOD:REPLY? It’s only possible that it keeps it as an “unknown property” when it has received it from the server.