For SLE 15 SP5 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/home:fschnizlein:branches:systemsmanagement:SCC:RMT/SLE_15_SP5/home:fschnizlein:branches:systemsmanagement:SCC:RMT.repo
zypper refresh
zypper install rmt-server
For SLE 15 SP4 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/home:fschnizlein:branches:systemsmanagement:SCC:RMT/SLE_15_SP4/home:fschnizlein:branches:systemsmanagement:SCC:RMT.repo
zypper refresh
zypper install rmt-server