Yup, works on Debian too. For future users, before a patch has been deployed, this solved it:
Run as root:
/var/lib/cmk-agent/scripts/cmk-agent-useradd.sh
/var/lib/cmk-agent/scripts/super-server/setup trigger
You could then reboot the server or manually restart the services as root:
systemctl restart cmk-agent-ctl-daemon.service
systemctl restart check-mk-agent.socket