The Radicale Project is a complete CalDAV (calendar) and CardDAV (contact) server solution. It aims to be a light solution, easy to use, easy to install, easy to configure.
CalDAV/CardDAV path: / (e.g. https://server.example/radicale/)
If well-known URLs are not configured (well-known section in configuration file), you can try /user/ (e.g. https:// server.example/radicale/user/).
Contact group method: groups are per-contact categories