I was looking for a way to join Ubuntu 20.04 to my UCS domain without a dependency on Join Assistant, and make it a bit more generic for maybe other distros? I wrote a script today, based on this documentation: https://docs.software-univention.de/domain-4.4.html
The script actually makes the computer show up as “Linux” under the Computers section of the UCS Web GUI, which was a problem with a plain old SSSD join.
Here it is: https://github.com/ABotelho23/UCS_domain_join
If anybody wants to assist in tweaking it so it can work with maybe Fedora and CentOS (and others?) I’m willing to accept pull requests.