Для 16.0 запустите от имени root:
zypper addrepo https://download.opensuse.org/repositories/home:lrupp:roundcube/16.0/home:lrupp:roundcube.repo
zypper refresh
zypper install php8-maxminddb
Для 15.6 запустите от имени root:
zypper addrepo https://download.opensuse.org/repositories/home:lrupp:roundcube/15.6/home:lrupp:roundcube.repo
zypper refresh
zypper install php8-maxminddb
Для 15.5 запустите от имени root:
zypper addrepo https://download.opensuse.org/repositories/home:lrupp:roundcube/15.5/home:lrupp:roundcube.repo
zypper refresh
zypper install php8-maxminddb