Excellent information - one less red herring.
So WiFi with your particular router and settings simply does not work with the C2 is a fair description?
Not even a listing of the band?
Then whether the band is global or local is something that is pretty easy to look up.
(But with the potential loss of sim region info through flight mode being out of the picture, this theory goes to the bottom of the list).
That’s a good point of observation. I don’t know enough about how the backwards compatibility works to give suggestions on how to proceed.
But other WiFi6-or-lower devices work fine i assume?
As a real-world example (though unlikely to be the issue); the router being out of ip addresses.
Many “only” give out 155 different addresses, often split across permanent and dynamic ones together.
All OSes pretty much do this.
It isn’t great; but it is a lot better than the inverse - i.e. not showing the user that there is a physical link but “only” lack of addressing.
I don’t immediately see any suspicious changes between these versions unfortunately.