

Not using GE-Proton9-2 will lead to pre-rendered cutscenes having showstopper issues (e.g. non-progressable black screens, "TV color test" screens, etc). This is the most up-to-date Proton/GE that fully works in my tests.

WINEDLLOVERRIDES='dinput8.dll=n,b' %command%
Download and apply the following to fix Ma Chao Musou attack. Once that is done use the attached launch options to make this work. https://community.pcgamingwiki.com/files/file/2924-fixed-the-problem-of-warriors-orochi-3-ultimate-ma-chao-musou-causing-the-enemy-to-go-black/
Proton GE is required to get the cutscenes to work.

WINEDLLOVERRIDES=dinput8=n,b %command%
Swapped the confirm button in the settings
Set TDP to 12
Black boxes during musou attacks
Grabbed the Warriors Orochi 3 fix from https://community.pcgamingwiki.com/files/file/2924-fixed-the-problem-of-warriors-orochi-3-ultimate-ma-chao-musou-causing-the-enemy-to-go-black/ since the OLED, even setting the refresh rate to 60 doesn't fix the black musou artifacts. Other than that, game runs perfectly.

Use a terminal script to switch screen refresh rate from 100Mhz to 60Mhz and back again after WO3 is closed, since anything over 60MHz causes graphical issues (black boxes). This isn't a Proton problem, it's a "ported badly" problem.
Screen refresh rates over 60Mhz cause black boxes to appear.
All the problems I had (and had to tinker to fix) are due to the poor port of the game (they also appear while playing on Windows).
Works perfectly fine out of the box - all of the bugs and problems I encountered are not related to running the game on Linux.
This worked perfectly before recent updates, and needed tinkering as described below to return it to perfect working order.
rapid micro side to side juddering of whole screen. Essentially unplayable in this state as it was so unpleasant. Solved below.
Needed to pick "windowed" or "borderless" (sometimes choose one then the other) from in game options>graphics settings menu to prevent juddering described above from occurring. Which options appeared from "windowed", "borderless" or "full screen" seemed to change depending on unknown factors and "windowed" did not appear when in steamOS beta channel and it was impossible to stop the juddering when in steamOS beta channel. I was only able to stop the juddering by stopping the game and reverting to steamOS stable channel then starting the game. Prior to recent updates it had been working well in steamOS beta channel too.
If proton 8.0-1 was not the selected compatability option, crashes occurred which required the deck to be powered off and on again.
Current state requires proton 8.0-1 to be selected in compatability AND requires stable steamOS channel to enable the selection of "windowed" in graphics options to make playable
Once in game change the display mode (in graphics settings) to borderless. Plus the resolution to 1280x 720 as it'll be 640x 360 by default.
Screen looks like it's vibrating.
Fullscreen causes the vibrating image. Change to borderless.
Game runs well after those two changes.
Switch desktop mode it runs perfectly. in game mode screen is shacking.
Ran fine with no problems, just had to change the resolution as it defaults to the lowest resolution possible.
Set Vsync to 30 fps; Manual GPU Clock set to around 1100MHz; TDP limit 5W
Cutscene no sound
Locks to 30fps in game(not through deck setting) to have relatively better experience and long playable time. The TDP limit can be further adjusted to have longer playtime. One may have a better experience than the PS3 version of the game.

Limit refresh rate to 58 due to the v-sync issue.
V-sync is locked at 57 or 58 instead of 60. Maximum resolution is bounded at 1280x768.
I use simplified chinese as game language.
Runs great even in splitscreen! Solid 58 fps after very minor tinkering! Biggest issue is cutscene audio is desynced.
Audio isn't synced in cutscenes but they're still easy to follow just mute the audio if it bothers you, most of the story plays out in visual novel style scenes anyway
The game runs on proton experimental Title screen is a test pattern though you can go past it fine Set refresh rate and fps to 58 or lower in the deck ui
If you have microstutter toggle between windowed and borderless in the in game options and it will go away until you close the game
In game runs at solid 58 fps even in splitscreen, if playing on a external monitor or tv use steam FSR to upscale without losing performance
The gameplay was spot with a consistent framerate and the story is mostly told through voiced text sequences. Overall a good experience.
Video playback had no sound and some in game cutscenes had slighly delayed audio. offical proton shows no video.
Honestly just fix cutscene playback and this and many other games will be 100%