obs-server from home:M0ses:branches:OBS:Server:Unstable project
Select Your Operating System
Add repository and install manually
For 15.6 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/home:M0ses:branches:OBS:Server:Unstable/15.6/home:M0ses:branches:OBS:Server:Unstable.repo zypper refresh zypper install obs-server