I have a power line going to my PC upstairs, Stadia doesn't seem to work with it, even though the speed is fine, I just get stuck on the checking network connection spinner in the bottom left.
I am using stadia together with my powerline. It works great for me.
If course it depends on you local conditions but I can play fine.
I would still wish for lower pings, but I think for this I would have to move somewhere else.