Hi everyone, I just received my UDM-Pro today and am really happy with it however, it is unable to use BT FTTC as an internet source. It is using a 4G modem at the moment however, I'm in a contract with BT and would like to use that. I am using a BT Business Hub in bridge mode to allow me to connect to BT via PPPoE. The UDM-Pro manages to login and get a public IP from BT however, it does not display service provider, uptime, location, also, it does not use it and declares it offline. I hope somebody could help me with this annoying problem!
I realise that this reply is 20 months after the question was posted, but an answer may still be useful to someone.
I use a UCG-Ultra, but I'd suggest that in this context it operates in a very similar fashion to your UDM-Pro.
I use a Huawei EchoLife HG612 vDSL modem instead of the BT router configured as a bridge, and this has no trouble in passing on to the router the information you mention.
These modems are seriously EOL now and are also limited to a maximum download speed of 100Mbps if memory serves, but hey, they work!
You might find that using a crossover cable between the modem/bridge and your UDM-Pro fixes the problem too, as some vDSL modems and bridge configurations seem to require this.