I get the impression that sabre/dav markets itself more as a platform on which one can build their own CalDAV/CardDAV applications.

I run it standalone, because I wanted a CalDAV system that could integrate with my local FreeIPA domain via LDAP. The only other project that met this requirement was davical [1], but it seemed much less active.

I ended up writing my own FreeIPA/LDAP authentication and principal backends [2] for sabre/dav. I believe they have a PDO backend built in, if you want to store your users in a database.

Basically, you composer install sabre/dav and wire all the components together in server.php. You'll also want to redirect the /.well-known/{caldav,carddav} URLs with a rewrite rule in your webserver. Most of this is described in their documentation [3].

If you're looking for turn-key solution with an administration GUI, you probably want Baikal [4], which is based on sabre/dav.

[1] https://www.davical.org/

[2] https://github.com/sacredheartsc/sabredav-freeipa

[3] https://sabre.io/dav/gettingstarted/

[4] https://sabre.io/baikal/