Same issue (I think)
I have one of the newer 4k Arris Freesat boxes but it would not accept the Ethernet cable. If I tried to search on WiFi it just trashed the Internet connectivity on WiFi.
I tried all the "separate networks etc"
Freesat would connect to my Hotspot so I could rule out things like "name of SSID" or "characters in password"
My eventual fix was to plug back in my Tenda Mesh - setup a wireless on that called "xxx-freesat"
and Freesat connected to that no issue - and all seems OK.
Even though that Arris Freesat is maybe only 4years old - seems the Ultra 7 is just too smart for its own good
so I guess you can try similiar if you have any old Access Point / Mesh / Router that can sit between Freesat and Ultra 7.
The only thing I was yet to test was if a Cat6 Ethernet cable would have any more luck than my old Cat5 - and maybe that would let Ethernet work.
But TBH - at this point - it works - so I will just live with that I think.
