UCS 5.0 Domain joining - fresh install

I’ve just spent a few hours trying to install UCS 5.0 via iso into Linode as a custom build.
Linode docs are very helpful and while some issues around mounting the iso etc, the install completed, and not really the issues I hit.

First issue;
Domain Join - As I had performed an AD take-over a couple years ago from SBS 2011(messy messy), and progressively updating/upgrading to 5.0 I wanted to join this new build to the domain.
I thought this would be a UCS Domain, but it fails to see the domainmaster even thought the DNS entry exists.
So I tried AD Join, in which was successful, but not what I wanted though.
The question here is, Once a AD Take-over has been done, how to you convert to a pure UCS Domain?
Second issue:
Hostname - As I came to the end of setup it asks for hostname, ok makes sense, but the name I wanted contained 2 “-”, like prod-ucs-lin01, and the setup would not accept this, but it would accept ucs-lin01.
I find this very odd, as Debian has never has this sort of limitation.
Is this a bug possibly?
Further frustration, in which a few posts around changing the hostname seems to be an issue, if you can’t set the right hostname in the setup, why is there no option/steps to change the hostname?

Thank you for your help.


Ok So I found something else about the 2 “-”, this does seem to work, but you must have “ucs” as part of the first letters of the hostname.
This seems an odd restriction, maybe a Univention Staff member can shed some light on why this is please?