Hey all,
thank you ever so much for helping me with this topic.
I finally found the solution. And yes, it’s a pretty strange one. In fact also the Windows 11-system started to run very unstable and began to lose it’s network connection every now and then.
While I was thinking about it while cleaning the living-room just in order to free my mind again a little bit, I thought, that this might be the problem: DUST! And that’s what finally worked out. As you might imaging I bought a used NUC and guess what: The ethernet-port was just dirty.
So I cleaned it up properly with some alcohol and q-tips and that made the deal. It’s up and running now for quite some time (crossing my fingers that this lasts for a while) and it’s now installed via the roon-image.
So, thanks again and sooooorrryyyy for bothering you all.
All the best from Germany. - Sterni