My question is, what settings are you using?
Viewing post in Could we get Steam Deck/Linux support?
Resolutions - 1280x800 (Steamdeck's native resolution)
Screen Resolution - 90%
View Distance - 3
AA - 1
PP - 2
Shadows - 0
Textures - 1
Effects - 2
Foliage - 1
Shading - 1
Volumetric Lighting - Off
Tonemapper - 1
Computer FPS - 30
But as lyghters pointed out, if you do have to have every light in the base on and you stand with every computer terminal in view, your FPS could drop to as low as 40.
And of course, if you can't get above 24 no matter what the settings are, it's your save.
Oh, 1 more thing. If even new games can't get to 60, your whole data file might be borked, and for that there is a Regenerate Data button in the options.