For openSUSE Tumbleweed run the following as root:
zypper addrepo https://download.opensuse.org/repositories/home:wolfi323:branches:KDE:Unstable:Extra/openSUSE_Tumbleweed/home:wolfi323:branches:KDE:Unstable:Extra.repo
zypper refresh
zypper install kstars
For KDE Unstable Frameworks openSUSE Factory run the following as root:
zypper addrepo https://download.opensuse.org/repositories/home:wolfi323:branches:KDE:Unstable:Extra/KDE_Unstable_Frameworks_openSUSE_Factory/home:wolfi323:branches:KDE:Unstable:Extra.repo
zypper refresh
zypper install kstars