
For one cutscene
Some slowdowns in the alien world
The opening scene works fantastic, getting your hopes up for a great gaming experience, once in the house though all goes to pieces.
Heavy motion blur due to low Frames per Second
After the initial "dream sequence" where everything works perfectly and the FPS is 60... when you get to the house, the FPS drops to 4 FPS on High and 7 FPS on Low settings. It makes it really difficult to move around, look at things and open drawers as every movement takes 20 seconds. The motion blur is also really heavy where you see more blur than sharp.
The game gets really laggy in the house and doesn't react to esc on the keyboard for 30 seconds or more.

Runs perfectly!
Not sure why others are having problems, I have experienced zero issues. The game runs great for me via Proton Experimental.

Works fine with Proton Experimental
When you start the game inside the house, my fps just drop a little, but not a big problem
I get a black screen after Sabinian says to take me to rest after I ingested the concoction. I tried with proton 5.13-5 and proton-ge-custom 6.0-GE-1
Proton Experimental worked fine, no problems and no black screen.

almost flawless.
Connected Controller disables the mouse and makes the game uncontrollable. Restarting without the controller works well.
The glossy textures in Lustt'ghaa sparkle from just minor camera movements, not sure if the sparkling is intentional or not.
If you have a controller plugged in, the game wont automatically detect your mouse/kb and you need to restart the game.
Right after waking up from the initial dream fps drops to below ten and the game becomes unplayable.
From the mansion onwards the game engine slows to a crawl and it becomes unplayable.

For a gamer on Linux, the game would be enjoyable until that black screen issue.
I get a black screen after Sabinian says to take me to rest after I ingested the concoction. I gave it a try for 20 minutes. Remains black. Tried restart, reboot. Did not fix.
Couldn't keep playing after the Ritual scene due to a black screen that wouldn't go away.
besides the mentioned crash everthing runs just like on windows
after the "'ritual" part it is just suck in a black screen
Black screen after the ritual
No sign of life at all aside from some idle processes in htop that are assigned to steam/proton
It is an enjoyable experience for the part that can be played.
After the ritual it just shows a black screen.
You can not complete the game
The game fails to playback cut scenes which will stop you from playing further after the "Ritual"
Missing video playbacks
Lacks serious performance optimizations after the first scene.
First act plays flawlessly > 60fps. From the mansion onward the performance falls drastically, to 7fps.