Thanks @ogs. I should mention, just in case it wasn’t obvious that udp-proxy-2020 also supports Roon devices on multiple local subnets/VLAN’s- not just OpenVPN tunnels.
It should also work on pretty much any VPN tunnel assuming your router/firewall pre-configures the network interface for inbound VPN tunnels. This prevents it from working with certain IPSec configurations which don’t use virtual tunnel interfaces, but I figure most people would rather use OpenVPN than IPSec+MOBIKE so probably not the end of the world.