It might help others how to configure Serial access to your server
In my case my UCS-servers are often running as a VM in some cases as a FreeBSD bhyve vm in other inside proxmox.
the articel from 2017 is not valid anymore as the system is now using systemd (no inittab anymore)
Unfortunately, I can’t edit this kb article, it is not allowed anymore. Maybe someone from Univention support could update? (or allow to edit this article: It would be a pleasure for me to contribute and to keep the article up to date)