Recently, there was a Steam Client beta update where the Nintendo Switch Joycons became officially supported by Steam. I am sure I wasn't the only one who thought about the possibilities with the Steam Deck, but unfortunately, it is a little different on the Steam Deck. While it does work well for the Steam Client Beta, the Steam Deck has a different client that receives updates slightly differently.
To use this at all, you need to be on the Steam client beta. If you are on a computer using the desktop Steam Client, go into your settings and switch to the beta. Then, you will want to go into Big Picture mode and into your controller settings. I would enable all of the options there, if you haven't already, and then restart Big Picture if it asks you to. Now, if you connect them via Bluetooth, (hold down the sync buttons between the SR and SL buttons to start pairing), it will recognize the controllers and work!
The Deck does recognize them if paired with the Deck through Bluetooth!
Now the options are still there on the Deck, but it doesn't work as well. After enabling the settings the same way, the Joycons are recognized. In Game Mode, they are recognized as two separate controllers though, so it turns them onto their side.
The system automatically recognizes the Joycons sideways and won't put them together as one controller. This makes playing most games near impossible.
You can change the controller layout for them, but they aren't recognized in Steam and have the name "Generic Controllers". Due to each Joycon being separated, I wouldn't waste the time to configure them. There aren't enough button inputs on one controller for most games.
The controller layout setup for generic controllers. May need a bit more inputs than one has though...
Hopefully this will be added to the Deck in the future though! Using Joycons would be quite nice if possible.
While the controllers aren't ready to be used on Deck, games are still being verified on Steam left and right! Check out our list of recommended games from the latest batch of verified games.