For openSUSE Tumbleweed run the following as root:
zypper addrepo https://download.opensuse.org/repositories/home:rrahl0:upgrades/openSUSE_Tumbleweed/home:rrahl0:upgrades.repo
zypper refresh
zypper install lutris
For 15.6 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/home:rrahl0:upgrades/15.6/home:rrahl0:upgrades.repo
zypper refresh
zypper install lutris
For 15.5 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/home:rrahl0:upgrades/15.5/home:rrahl0:upgrades.repo
zypper refresh
zypper install lutris