Steam's verification badges are a good starting point for a game's playability. For more information, or to confirm if a game can actually be played when Steam says otherwise, give ProtonDB a look.

Valve has done well at making the Steam Deck a 'play things out of the box' experience but there may be occasions where you'll need to do a bit of tinkering. If that happens there's thankfully a lot of good community resources out there to help you work through it.