Para 15.6 corra o seguinte como root:
zypper addrepo https://download.opensuse.org/repositories/home:tlusk:kubectl/15.6/home:tlusk:kubectl.repo
zypper refresh
zypper install k3d
Para 15.5 corra o seguinte como root:
zypper addrepo https://download.opensuse.org/repositories/home:tlusk:kubectl/15.5/home:tlusk:kubectl.repo
zypper refresh
zypper install k3d
Para 15.4 corra o seguinte como root:
zypper addrepo https://download.opensuse.org/repositories/home:tlusk:kubectl/15.4/home:tlusk:kubectl.repo
zypper refresh
zypper install k3d