i run on a new-ish high end system, fedora 37, steam, proton, no changes made by me
worked out of the box, of course with tons of bugs.
with a simple rocket 4k highest settings seems well playable, once you get away from ksp it is perfect.
16gb vram amd and amd threadripper, 3 digits of ddr4 ram, quad channel
however large complex rockets make the game unplayable fps wise. i'm not an engineer, but the game does seem to use a fraction of what the hardware could provide. that was before the patch. a little better after the patch, not very much yet.
however:
the worst of the worst is a bug that persisted from before the patch and got 1000 times worse with the new patch, rendering the game entirely unplayable: long press inputs such as steering a rocket completely messes up the input queue of the game engine. 5 seconds pressing left translates to 15-25 seconds of pressing left, ignoring all inputs until that now way too long steering input is completed. after that it executes all key presses one after another, from map on off on off on off to esc menu on off on off on off to time ,.,.,. but if you press right to counteract the over steer that was induced, the problem compounds and the game gets worse and worse and worse.
at some time you just watch the game seemingly played by somebody else, of course since esc is not even elevated over other key inputs in ksp2, pressing that does nothing during that time.
the very first time starting with the new patch no steering input was accepted at all. then i updated everything (os, steam, those vulkan shaders steam sometimes updates, restarting for the new kernel, opening and then closing ksp2, then finally reopening ksp2 and start testing) and now i am left with this mess i described above that makes ksp2 unusable.
i hope this gets better, it could be such a great game. btw i only do rockets. i am not interested in the planes at this time.