I have a SYNOLOGY DS218 play.
DAVx5 worked very well when I was under LineageOS 15.1, i.e. Android 8.1.
Since my time on LineageOS 16, Android 9, I have been having problems.
I have 2 accounts to synchronize. When I set up my A account, I only have access to CardDav and no more CalDav. I can no longer also synchronize my B account.
Strangely, when I reset DAVx5, I can configure my account B but no longer my account A. And I still don’t have access to my calendar. However, I followed the instructions here https://www.davx5.com/tested-with/synology/.
I get a message when I try to configure my 2nd account “No access possible CaldDAV or CardDAV.”
Here is the detailed message davx5-info.txt
If you have any ideas, I’m a buyer