PROTON_USE_WINED3D=1 %command%
Mapped back butttons L4 and R4 to mouse keys
40hz refresh rate
Proton 6.3-8 & Wine3D are needed for the game to run, as it would shown endlessly a blackscreen when encountering a video. Videos are not relevant for the game and can be skipped once the appear.
Patch can be just installed via Drag n Drop.
At the first Tsuchigumo fight, the vn will hang as it attempts to play a video. Unlike with Proton 6, PROTON_USE_WINED3D=1 %command% does not fix that.
PROTON_USE_WINED3D=1 %command%
with Proton GE 6 the vn is playable from start to finish. there is no native controller support, so remapping for mouse functions is necessary when playing with one. the dualshock 4 touchpad can be used by default.
Blank screen on startup, but music plays. Cannot continue after that.

Proton-6.21-GE-2 GloriousEggroll
To get something else than a black screen when starting the game rename the folder "video" into something else. Movies won't play but it isn't a loss, they can be watched in the video folder. The movies are 4 very short character animations, the logo of the company and the opening.
You'll still get a black screen, just click a couple of times.
Roughly two hours in the game an animation should play and the game crashes. To fix that install quartz (might be unnecessary) via protontricks and (necessary) use PROTON_USE_WINED3D=1 %command%
I have not encountered any further problems.
Don't disable Esync, the game gets very slow when you do.

Opens a blank window for a few seconds then exits. Nothing seems to help.