Opensuse hasn’t been able to use rwho and ruptime or show up in the rwho and ruptime reports of other hosts because it lacked the necessary rwhod daemon. This daemon was not part of the OpenSuse distribution and thus not available to install via Yast.

     I found a version that worked on rpm.pbone.net and installed it, created the necessary firewall, user, and systemd entries, and it is now operational.