I might be misinterpreting this, if so my apologies, perhaps you could elaborate further.
The Hegel H190 should be connected to a network switch via RJ45 not directly to the MacBook.
Also for best results Roon recommend that devices running the Roon Core are hardwired to the network via RJ45 rather than Wifi (it’s also avoid Powerline adapters as well).
Yes the Hegel H190 is connected to a network switch via RJ45.
The core (on MacBook Pro) also is connected to this network switch via RJ45.
All hardwired – no WiFi.
Then it remains to check that IP addresses for the MB and 190 are in the same network. Like 192.168.0.xxx or 10.0.0.xxx for both. If they are and it still doesn’t work, check that cables are good.
EDIT: is the switch manageable or is it a “dumb” one?
I see the message, "No Audio Devices Found.
Underneath there is the button, “Manage audio devices”
After selecting that button, there are several outputs to ‘enable.’ Under ROON, the Hegel H190 is not an option. (I have updated the H190 to latest software version, which is RR.) The H190 is not shown.
Even if it’s not showing up as Roon Ready, it should be there as an Airplay device that can be enabled, as shown for my H390 (which is not RR yet). Do you see this? Also is the little tick mark showing on the H190’s display meaning it’s connected to the network?
Yes, I’ve rebooted everything – multiple times!
I attempted to change the IP address on the Hegel H190 – but it’s too complex for me (subnet mask, etc) so no news about that…
I get that Airplay is not ideal, but if your H190 is properly connected to the network you should be able to see it as an Airplay device in Roon as per my screenshot, and there should be the little tick mark showing in the H190 display. If you can’t see those, there is an issue with your H190 connecting to the network, which could well be some IP address problem.
Good news. Have you checked the volume controls in Roon (after turning down the volume on the H190) as shown below - bottom right of the play control screen? By the way, I’d strongly recommend setting a maximum volume on the H190 to something like 65 to avoid any nasty surprises.