Licquorice, they supplier says that is necessary because -
IGMP Snooping This should be on as it groups the device broadcasting Multicast traffic ( the Player ) with the device looking for that traffic ( the Controller ) Some devices operate Multicast traffic more efficiently without having this setting on so you will need to see what performs best based in your specific network environment. (there is nothing on the Smart Hub that says whether it even exists never mind for me to decide whether it should be on or off)
Multicast This should be on and not restricted as this is the network protocol we use for discovery.
They have the Archer C9 working, so simply it works. The Archer C9 was what they informed me was working. They didn't recommend it, simply used it as an example of a modem/router that worked with their kit.
OK I wanted to add few things to this post to help others. First I don't know for sure if the new BT Smart Hub supports IGMP snooping and Multicast since I don't use one. But considering that all the additional non-freeview BT channels (like BT Sport) transmit only via multicast it will be inconceivable to think that the new BT Smart Hub didn't support IGMP snooping and Multicast. On this thread this statement was made: "Multicast is not transmitted over the wireless network". I beg to differ, I would say that if you are using a BT Home Hub or BT Smart Hub and you connect the BT TV box directly to it then yes, multicast traffic will not be transmitted over the wireless network. But other network topologies can easily cause multicast traffic to end in your wifi network. It's also worth mentioning that depending on your network topology IGMP snooping alone might not be enough in keeping your multicast traffic off the rest of your network. I have detailed the issue I had and how I solved it on this post. Hope it helps others!