For openSUSE Tumbleweed run the following as root:
zypper addrepo https://download.opensuse.org/repositories/KDE:KDE3/openSUSE_Tumbleweed/KDE:KDE3.repo
zypper refresh
zypper install kde3-kmplayer
For openSUSE Leap 15.1 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/KDE:KDE3/openSUSE_Leap_15.1/KDE:KDE3.repo
zypper refresh
zypper install kde3-kmplayer
For 15.6 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/KDE:KDE3/15.6/KDE:KDE3.repo
zypper refresh
zypper install kde3-kmplayer
For 15.5 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/KDE:KDE3/15.5/KDE:KDE3.repo
zypper refresh
zypper install kde3-kmplayer
For 15.4 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/KDE:KDE3/15.4/KDE:KDE3.repo
zypper refresh
zypper install kde3-kmplayer