I had the same problem and I could (apparently) run the join scripts - there are no scripts shown as pending.
I had to manually add ucs-sso.MYDOMAIN to the DNS, then execute the script from https://help.univention.com/t/idp-metadata-univention-run-join-scripts/3717/4.
However, there are still errors while executing these commands.
is yelling about certificate errors (as shown in the first post in this thread) - certificate is not trusted, it had been issued by an unknown publisher and it doesn't match the hostname.
only warns about the certificate problems, but then, for the HTTP request, there's a "404 Not Found" error.
So, is there anything I should do here? Or can I ignore the described problems?