For openSUSE Tumbleweed run the following as root:
zypper addrepo https://download.opensuse.org/repositories/home:bjoernv:branches:home:Herbster0815:HTPC/openSUSE_Tumbleweed/home:bjoernv:branches:home:Herbster0815:HTPC.repo
zypper refresh
zypper install hd-idle
For 15.6 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/home:bjoernv:branches:home:Herbster0815:HTPC/15.6/home:bjoernv:branches:home:Herbster0815:HTPC.repo
zypper refresh
zypper install hd-idle
For 15.5 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/home:bjoernv:branches:home:Herbster0815:HTPC/15.5/home:bjoernv:branches:home:Herbster0815:HTPC.repo
zypper refresh
zypper install hd-idle