I Changed the resolution to 1024x640 in the steam launch options so I could use fsr and have a semi stable 30fps cap. I set almost all settings to low except texture quality and turned off ambient occlusion, screen space reflections and volumetric lighting. There will be dips to the low 20's when breaking multiple barrels at once or fighting lots of enemies at once.

The steam deck will struggle at the default resolution of 800p, making the resolution lower and using fsr will help but will also mess with how text looks some. As long as you're not too picky about dipping below 30 fps you'll have a playable experience. I also set the mangohud fps limiter in the launch options as the built in steam frame limiter had a habit of not actually locking the framerate down and I'd have to re-toggle it to make it work again, frankly just easier to set a launch option and not have to think about it.