If it's of any reassurance I have had Sky Q with 2 mini boxes for 8 years, I have never hard wired any of them, I have a decent size house but definitely not thick walls, all 3 boxes are connected wirelessly to BT Wholehome mesh Wifi. My internet and router is provided by Gigaclear Fibre to the premises 600mbs but I disabled the wifi on the Gigaclear router and use BT Wholehome instead (the original version - 6 discs).
Generally Sky Q is troublefree for me, but my word, when they decide to go wrong they do it in a really big way! Be ready to spend a couple of days getting them back up and working reliably when it goes wrong. I have had engineers here a couple of times years ago, but usually their config (using the in built sky mesh wifi) has failed quite soon after they leave. I now always reconfigure the mini boxes on the BT mesh wifi.
In my house, I can move the furthest of the mini boxes 2 foot further away and both mini boxes will go into error mode e.g. no internet or no broadband, or no sky q activation.
So when troubleshooting connectivity I always put all 3 boxes close together first just to ensure they can indeed be reconfigured and there is no other fundamental issue. It's as if they must still communicate with each other over their own Sky wifi (perhaps related to proving the sky q activation process), as it shouldn't really be an issue if they did this over the BT mesh wifi, as with 6 discs in the house the BT signal is strong everywhere.
Also making a change on any sky box or even recycling the power, you can easily go down a rabbit hole of tweaking and changing stuff to try and get the damn things to connect but nothing seems to work!
Experience has shown they seem to take ages to configure themselves after any tweak or interruption they just continually error, I just leave them for 30 minutes or an hour and surprisingly often the errors go away and they have magically reconnected.
What I've learnt would take days to write down, but some fundamentals are:
Don't follow any troubleshooting prompts from the Sky mini boxes.
Have patience and wait a period after any change.
Always ensure the main box is stable first, the mini box errors can take you down another rabbit hole when often it's the main sky box.
Turn off the mini boxes and leave them until main box keeps a stable connection on wholehome (If the main box has wandered away from it's usual closest BT disc then try and force it back to the disc you know it works on).
In my house I can guarantee that if the power goes off or there has been any disk interupted on BT mesh wifi then Sky will go into error mode while every other device on wifi in the house will return and work perfectly normally - but not Sky Q. Any errors with Sky and out of habit I always go and look at the BT Wifi disc config first.
Just a week ago this happened to me again (I had to turn off mains power in the house which caused all the BT discs to auto reconfigure when switched back on) and it took me 2 days to get sky all back, working and stable - but I knew beforehand it would be an issue - they are all working fine again now.
As I say, I have never hard wired mine so can't help in that case but thought I would share my experience that generally they work well but are painful when a glitch occurs and they can't reconnect.
Best of luck!
