My Nokia 7+ got just upgraded to Android 10, and the Roon app failed to find the server.
The assessment that this is due to a misconfiguration of the network is probably incomplete. This particular network is a flat subnet with no restrictions. Note that I am not running a Nucleus; I am running Roon from a NAS (which could be part of the issue).
If you want, I can do some troubleshooting in my network to see if we can nail it down.
usual multicast/broadcast based discovery mechanisms are not working.
This is vague. What protocol are we talking about here, except the ARP issue?
Finally, can I suggest that you update the Roon Android app on Android 10 to notify users of this potential problem when the Roon server cannot be found?