Para 16.0 execute o seguinte como root:
zypper addrepo https://download.opensuse.org/repositories/server:Kolab:16.3/16.0/server:Kolab:16.3.repo
zypper refresh
zypper install roundcubemail-plugins-kolab
Para 15.6 execute o seguinte como root:
zypper addrepo https://download.opensuse.org/repositories/server:Kolab:16.3/15.6/server:Kolab:16.3.repo
zypper refresh
zypper install roundcubemail-plugins-kolab
Para 15.5 execute o seguinte como root:
zypper addrepo https://download.opensuse.org/repositories/server:Kolab:16.3/15.5/server:Kolab:16.3.repo
zypper refresh
zypper install roundcubemail-plugins-kolab