For test run the following as root:
zypper addrepo https://download.opensuse.org/repositories/home:gmbr3:Active/test/home:gmbr3:Active.repo
zypper refresh
zypper install gn
For openSUSE Tumbleweed run the following as root:
zypper addrepo https://download.opensuse.org/repositories/home:gmbr3:Active/openSUSE_Tumbleweed/home:gmbr3:Active.repo
zypper refresh
zypper install gn
For openSUSE Factory ARM run the following as root:
zypper addrepo https://download.opensuse.org/repositories/home:gmbr3:Active/openSUSE_Factory_ARM/home:gmbr3:Active.repo
zypper refresh
zypper install gn