For openSUSE Tumbleweed run the following as root:
zypper addrepo https://download.opensuse.org/repositories/home:Simmphonie/openSUSE_Tumbleweed/home:Simmphonie.repo
zypper refresh
zypper install mkvalidator
For openSUSE Slowroll run the following as root:
zypper addrepo https://download.opensuse.org/repositories/home:Simmphonie/openSUSE_Slowroll/home:Simmphonie.repo
zypper refresh
zypper install mkvalidator
For 16.0 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/home:Simmphonie/16.0/home:Simmphonie.repo
zypper refresh
zypper install mkvalidator
For 15.6 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/home:Simmphonie/15.6/home:Simmphonie.repo
zypper refresh
zypper install mkvalidator