The team has worked hard to ensure compatibility with Fastival on a Steam Deck. You'll want to tweak your settings a bit to get the game running well:

1. In the main menu, go to Settings > Video
   
2. Set the resolution to 1280x800 (the native Steam Deck resolution)
   
3. Set the graphics quality to Medium for ~60fps

The game's default 1080p on Epic will not run well on a Steam Deck, but once you make the changes above, it's a buttery smooth framerate.