I used the Sunshine game streaming software and the WiiU homebrew port of Moonlight to get game streaming working on a WiiU gamepad. It’s sort of like a bootleg Steam Deck, and it works surprisingly well, but it mostly just made me want a Steam Deck.
Slightly perceptible, but totally playable. Considering all the hops it has to make, it’s surprisingly good. I have both my WiiU and my desktop hooked up to ethernet, which helps. Games like Portal 2 work well because they don’t usually require split second inputs, but anything requiring precision (like a rhythm game) would probably be a struggle.