I just found out for me personally my issue with fps is due to number of lights turned on at the base. If I disable all the lights, my fps at the base is around 70-90 instead of 30-40. The more lights I enable, the less fps I get while I'm at the base. As long as I look towards the middle of the base. I don't need to perceive the light directly, walls and doors don't matter.
Viewing post in Could we get Steam Deck/Linux support?
No, it's not a performance issue.
The Steamdeck lets you open an overlay that gives you the details of exactly what your CPU and GPU are doing.. Eventually, the game will just decide to lock itself to 24 FPS, no matter how little the GPU or CPU are being used.
I could stand in an open field, with every detail set to 0, rendering at 25% resolution at 800x600, with an uncapped framerate, and still only 24 FPS. While a new save in the same spot with the same setting can get well into the 100s.
I'm not playing on a Steam Deck, I'm playing on PC on Linux. It is a performance issue. I just told you my FPS fluctuates between 30 and 90 depending on how much lights are turned on at the base.
I don't have any knowledge about Steam Deck or it's limitations, but even if your game is locked at 24 FPS, it changes nothing about what I say.