Please see https://forums.bitfire.at/topic/1674/what-is-the-2-letters-after-the-account-name-for-address-books and the links there (especially the manual)
Using Owncloud and DavDroid I tried syncing several contactlists with my Android device but managed only one.
With my recent CardDAV-App I could choose all the contactlists within the account.
Isn’t there any similar Option within DavDroid?
(Within the CalDav-Account of DavDroid it is working fine).
Please read https://davdroid.bitfire.at/faq/entry/only-one-addressbook/ and the related topics here.
Thanks, I didn’t find this one. Anyway, the app carddav manages several books at once, which is, I was looking for. Maybe you can integrate such a solution in future times. All the best!