For openSUSE Leap 15.3 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/security:SELinux/openSUSE_Leap_15.3/security:SELinux.repo
zypper refresh
zypper install selinux-policy
For SLE 15 SP3 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/security:SELinux/SLE_15_SP3/security:SELinux.repo
zypper refresh
zypper install selinux-policy
For SLE 15 SP2 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/security:SELinux/SLE_15_SP2/security:SELinux.repo
zypper refresh
zypper install selinux-policy