For openSUSE Tumbleweed run the following as root:
zypper addrepo https://download.opensuse.org/repositories/home:deltafox/openSUSE_Tumbleweed/home:deltafox.repo
zypper refresh
zypper install rawtherapee
For openSUSE Factory run the following as root:
zypper addrepo https://download.opensuse.org/repositories/home:deltafox/openSUSE_Factory/home:deltafox.repo
zypper refresh
zypper install rawtherapee
For 15.5 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/home:deltafox/15.5/home:deltafox.repo
zypper refresh
zypper install rawtherapee
For 15.4 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/home:deltafox/15.4/home:deltafox.repo
zypper refresh
zypper install rawtherapee