If you’re going to be using an external gigabit switch with your Sky Q Hub, make sure that the cable that connects between the Sky Q Hub and your switch uses a gigabit capable cable (e.g. cat5(e)/6). I know that sounds silly, but if you try a cable that’s only capable of Fast Ethernet (up to 100Mb), and you have gigabit devices connected to your external switch, you’ll run into problems with those gigabit devices. So make sure the uplink capable is a cat5/cat5/cat6. I don’t think auto-negotiation is quite right on the Sky Q Hub – hence pick your cable carefully.
So make sure your uplink capable is a cat5/cat5/cat6 cable.
PS – Sky Fibre Pro is now providing native IPv6 connectivity on the WAN port. So now you can browse IPv6 sites without the need of a tunnel broker. It’s not a static IP from what I can see (unlike my IPv4 address), but it’s better than nothing!