Working fine here as well with one caveat.
We need to use the php-sabre-dav and php-sabre-vobject provided with the
tar ball on github.
If the debian packages php-sabre-dav and/or php-sabre-vobject with the
versions packaged in Debian 12.1 are installed roundcube throws a
"Uncaught Error: Call to undefined method
Sabre\VObject\Component\VCard::getDocumentType()".
Documented also here: https://github.com/mstilkerich/rcmcarddav/issues/449
So.... tag as conflict with php-sabre-dav and/or php-sabre-vobject below
a certain version?
Cheers
Christopher