Valve's Steam Deck is a portable gaming PC through and through. It might be marketed as a way to play Steam games on the go, but at its very core, it's still a desktop. This means that you can use it as you would a regular old gaming computer, and this includes running emulators through them.
Valve admitted this in a new YouTube video, which it promptly deleted.
Most probably wouldn't have noticed Valve supporting emulation in its latest three-minute YouTube clip, but Nibel, a well-known industry insider, managed to capture the specific portion of the footage. Naturally, the tweet blew up quickly online and it appears that Valve nor Nintendo has taken any measure to take it down.
Valve has since replaced the video with a new one that swaps the Yuzu thumbnail with that of Portal 2. However, now that the cat is out of the bag, we're curious to see the fallout.
Technically, emulation isn't illegal. Otherwise, emulators like Yuzu shouldn't exist out in the open. This software, in particular, lets you play Switch games on other devices. Before the Steam Deck and other portable gaming PCs, you had to have a traditional desktop to use Yuzu. Now that this is no longer the case, the taboo subject of video game emulation will be the main topic in gaming circles again for the foreseeable future.