Xandikos

DAVx⁵ has been successfully tested with Xandikos.

Xandikos is a lightweight git-backed open-source CalDAV/CardDAV server.

DAVx⁵ settings

Base URL: the URL of the Xandikos server, e.g. https://xandikos.example.com

Contact group method: groups are separate VCards (or the method used by your other clients)