Steam Input now supports those lovely new Nintendo Online classic controllers, thanks to yesterday's patch. Steam Input is Valve's built-in software for letting people use whatever controller they like, and mapping the buttons and functions properly so a game recognizes them even if it only officially supports the Xbox gamepad.
The Nintendo Online controllers are re-releases of the classic Nintendo 64, NES, SNES, and Sega Genesis/Mega Drive controllers. They're for sale on Nintendo's online shop (though often sold out), and were intended to be used with Switch's subscription service, but the Switch uses Bluetooth, not some proprietary wireless tech. So clearly someone at Valve did what we were all thinking and made them work on PC. (Thanks, anonymous engineer.)
And, yes, this means you can go very far with your quest to pretend your Steam Deck is some kind of giant mutant Switch. You can recreate all those scenes from Nintendo marketing where someone's using the Switch on a table with two people playing local co-op with Nintendo controllers, except it's a Steam Deck. You can get started on doing that in our guide to setting up controllers on a Steam Deck.
The simple way to get this set up is to plug your fancy controller into your PC. From there, hit up Steam. Go to Settings -> Controller -> and hit up General Controller Settings if you haven't done this before or jump right into your chosen per-experience settings. If you need longer directions, we got those in our guide to how to use a Switch Pro Controller in Steam.
Nice spot, Eurogamer.