For openSUSE Leap 15.2 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/server:Kolab:16.0/openSUSE_Leap_15.2/server:Kolab:16.0.repo
zypper refresh
zypper install kolab
For openSUSE Leap 15.1 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/server:Kolab:16.0/openSUSE_Leap_15.1/server:Kolab:16.0.repo
zypper refresh
zypper install kolab
For openSUSE Leap 15.0 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/server:Kolab:16.0/openSUSE_Leap_15.0/server:Kolab:16.0.repo
zypper refresh
zypper install kolab
For 15.3 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/server:Kolab:16.0/15.3/server:Kolab:16.0.repo
zypper refresh
zypper install kolab