For 15.6 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/home:hibby50:server/15.6/home:hibby50:server.repo
zypper refresh
zypper install restic
For 15.5 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/home:hibby50:server/15.5/home:hibby50:server.repo
zypper refresh
zypper install restic
For 15.4 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/home:hibby50:server/15.4/home:hibby50:server.repo
zypper refresh
zypper install restic