I cannot help you with your SMT questions.

However you have to consider this statement "SLES 15 SP4 or later" if you want to go for GMS 24.1. So OES23.4 will fulfill requirements I think. Now. But what happens if GMS will go for newer versions of Sles?

Current versions of GMS (23.4 and newer) are supported running only on SLES 15 SP 3 or newer.  It also needs to be installed on a dedicated server, either VM or bare bones.  We do not support any version of GMS running on an OES server.  Please see the documentation here - https://www.novell.com/documentation/groupwise23/gwmob_guide_install/data/inst_req_server.html.  To receive the packages necessary to install Mobility, your SLES server must be registered or you must have a SLES Repository Mirroring Tool configured to provide them to the SLES server.

Yes, I read this in the requirements. And I have installed the GMS as describted.

After a installation of GMS there are four enabled repos at the SLES15SP4:

SLE-Module-Basesystem15-SP4-Pool   
SLE-Module-Basesystem15-SP4-Updates
SLE-Module-Python3-15-SP4-Pool     
SLE-Module-Python3-15-SP4-Updates

All is fine ... but the host were the GMS is running is not registered to my SMT.

In the OES-Env. I found these Repos are available, too:

OES23.4-SLE-Module-Basesystem15-SP4-Pool
OES23.4-SLE-Module-Basesystem15-SP4-Updates
OES23.4-SLE-Module-Python3-15-SP4-Pool
OES23.4-SLE-Module-Python3-15-SP4-Updates

I assume that the contents of the repos are equal.

So if GMS were on OES, It were able to register easily to the SMT and get the necessary packages from there. All related hosts were at one update service. I could stop the registration at SUSE, and so on.

And now I want to understand why OT needs a separate way to register, update etc. the GMS ...

Eliza - As far as I know, GMS has never been tested going to an OES SMT pool.  While I think it should work, I don't know for sure.  I would suggest putting that into the Ideas community for the product manager to consider.  - Pam