Thank you both @wizardofoz and @wklie. Unfortunately, I had no luck. I did what you suggested, but the issue remains the same. By the way, there is a “Tidal login failed” message, too.
If it were a networking issue, at least the internal/local interfaces of the NUC computer should appear listed as outputs, as those are not mapped or found over the network. Hence, it looks like something went wrong with the update on the RoonOS side to me, am I right?
Intel® Optane Memory H10 (16gb) with Solid State Storage (256tb) NAND
For Tidal, I re-logged in and it worked, but still no audio devices detected.
Do you think that reinstalling RoonOS and restoring from backup could work?
Rebooting after renaming RAATServer folder worked. I also deleted the Tidal account file. I also removed all temp files (not sure why I did it, just had the impulse of doing it as a recovered windows user with OCD )