Yes. Yes you can. Squad is currently Unsupported on Steam Deck, according to Valve because “This game’s anti-cheat is not configured to support Steam Deck”
This is a problem plaguing many games that you should easily be able to play on the Steam Deck. For months, Valve has been working with Epic on supporting Easy Anti-Cheat with Proton. As of January 2022, adding Proton (and thus Steam Deck) support to developers’ existing Easy Anti-Cheat games is incredibly simple. Steam offers a simple four step process to activating Easy Anti-Cheat support.
While we wait patiently for developers to decide to support Steam Deck, there are some workarounds available and Squad has a Silver rating on ProtonDB with many users playing online multiplayer with decent success.
If you’re interested in playing Squad on Steam Deck, consider reaching out to Offworld Industries and request that they enable support for playing Squad on Linux.