

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 (when bought outside of Steam).
During the fight with Len at the start, 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, including the extra stories. 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.
Videos don't play at all, an error screen is shown and after clicking a few times the game goes on so it ain't breaking the game. (But this only works guaranteed in Proton 6.3-8. I tried it in 4.15-GE-1, 6.21-GE-2 and 0rc3-GE-1 and in all of them the videos break the game (infinite blackscreen with music playing). If you want to use one of those versions you have to rename the video folder before launching the game. Rename it to the original after loading your save file because the game breaks in the fight scenes if there is no video folder.
Without WINED3D the animations in the fights will make the game crash so use
PROTON_USE_WINED3D=1 %command%