For openSUSE Factory run the following as root:
zypper addrepo https://download.opensuse.org/repositories/security:SELinux/openSUSE_Factory/security:SELinux.repo
zypper refresh
zypper install checkpolicy
For 15.6 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/security:SELinux/15.6/security:SELinux.repo
zypper refresh
zypper install checkpolicy
For 15.5 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/security:SELinux/15.5/security:SELinux.repo
zypper refresh
zypper install checkpolicy
For 15.4 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/security:SELinux/15.4/security:SELinux.repo
zypper refresh
zypper install checkpolicy