Different internet for Sky Q mini box

[Vicky+J01]

So I've just received the sky Q mini box.

My main box is up stairs using a tether router, as the router doesn't reach upstairs.

My mini box however needs the router down stairs but I cant change the Internet source.

Any way to change the Internet connection?

[Chodley]

"using a tether router,"

What is that? Mobile SIM separate router? No the mini has to connect to the same network as the Q to find it.