GT-MT3000 VPN Routing UDP to LAN Clients


I have a server running in my home network (Roon) that communicates with clients via UDP broadcast/multicast (not sure which).

To do this I use a tool called UDP Proxy 2020 (GitHub - synfinatic/udp-proxy-2020: A crappy UDP router for the year 2020 and beyond)

When I use Wireguard on my MacBook it works fine across the VPN and the Mac client connects to the server.

When I use the Wireguard client in my GT-MT3000 the Mac connecting to the router can’t connect to the server via the VPN.

What is happening? Is there blocking of the UDP broadcast/multicast happening between (Wireguard) and (GL-MT3000) networks?

I tried to change a firewall rule in LuCI that seems to drop anything going from Wireguard to elsewhere, but the rule doesn’t save or is overridden elsewhere.

I don’t know enough to debug or proceed so if anyone else has an idea I’d really appreciate the help.