InternetGatewayDevice:2 devices are not supported

[fishface60]

InternetGatewayDevice:2, WANConnectionDevice:2 and WANIPConnection:2 interfaces were defined to address issues with IGDs being used for DDOS attacks because they were misconfigured to accept discovery requests on the WAN link.
Amongst the changes is an assertion that you should only support this interface if you have ensured this behaviour.

Unifi devices do not advertise WANIPConnection:1 and instead only expose the version 2 of the interface, presumably to advertise they are correctly configured.