Great work! Amazing revamp.
For other's reference, I was able to get this up and running on Ubuntu Linux just fine with a couple of caveats using a 2070S and Proton with Glorious Eggroll config. Running about 50fps. That's with Astronomer's Visual Pack (8k textures), Scatterer, EVE, and TuFX running as well.
- Turn down antialiasing from 8x to 4x. 8x drops the framerate to a slideshow with Parallax.
- Half-res textures. Going to full res textures drops it to 5 fps for me.
- Turned off reflections completely
Everything else maxed. On native linux I can run with everything maxed and Parallax going, but obviously no Parallax scatters.
As others mentioned things did seem a bit darker than they should but that's the only issue I've noticed. This may be limited to planets with atmosphere, need further testing. Vall scatters did seem uniquely slow with only about 20fps there. Eve, Kerbin, and Duna all ran well.