I finally had some extra time to download the older 4.2.1 ISO. Installation went well (got one error popup which closed itself towards the end) and the system also updated itself during the process.
So far so good!
Now, there is one issue which has been there before. In the version I used before (4.2.1 or older), I would get a popup telling me saying “Internal Error: Could not connect to the module process. Server error message: Connection to module process failed” from time to time. In the new version (4.2.2.) I am getting it every time I logon. I also always get the initial popup asking me to approve feedback every time I logon and, yes, I have completed it the first time until the finish step came up.
So, there is still some kind of issue on my system.
That said, I was able to connect to an existing domain just fine. However, when I checked my DNS records, I only found a subset of the DNS settings of the domain server. Is this by design? It seems that it only copied AD related DNS settings, but I completely ignored all manually added A and TXT records.
If that is a separate issue, I can open another topic. Please let me know.