For openSUSE Tumbleweed run the following as root:
zypper addrepo https://download.opensuse.org/repositories/multimedia:apps/openSUSE_Tumbleweed/multimedia:apps.repo
zypper refresh
zypper install qmmp-plugin-pack
For openSUSE Slowroll run the following as root:
zypper addrepo https://download.opensuse.org/repositories/multimedia:apps/openSUSE_Slowroll/multimedia:apps.repo
zypper refresh
zypper install qmmp-plugin-pack
For 15.6 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/multimedia:apps/15.6/multimedia:apps.repo
zypper refresh
zypper install qmmp-plugin-pack
For 15.5 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/multimedia:apps/15.5/multimedia:apps.repo
zypper refresh
zypper install qmmp-plugin-pack