After a few tweaks, Swarmcade has now been officially Steam Deck verified!
Here are Valve's certification notes:
Valve’s testing indicates this title is Verified on Steam Deck. This game is fully functional on Steam Deck, and works great with the built-in controls and display.
- All functionality is accessible when using the default controller configuration
- In-game interface text is legible on Steam Deck
- This game's default graphics configuration performs well on Steam Deck
Value also recommends using Proton Stable to run the game.