The Steam Deck's controller is usable without Steam running, except for that long, looong pause when Steam has taken over the controller but isn't doing anything about it yet.
I wish that Steam would not put the mouse buttons on the triggers, just leave them on the trackpad-click. And put "high res trackpad scrolling" on the left pad. But you can't have everything.
Doesn't everybody play fighting games on "a piece of plywood with a bunch of arcade buttons jammed into it"?
Oh, and the backside buttons on the deck are pretty convenient. You might end up liking them more than having "more face buttons than your thumb can reach".