Baïkal

DAVx⁵ has been successfully tested with Baïkal.

Baïkal is a lightweight CalDAV + CardDAV server, based on SabreDAV.

DAVx⁵ settings

Base URL: /dav.php/ (e.g. https://server.example/baikal/dav.php/) or

Base URL: /html/dav.php/ (e.g. https://server.example/baikal/html/dav.php/) (in newer versions)

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