

Runs perfectly

I ran the game using Proton 9.0-3 and it worked great.

Back buttons for changing weapons
In some rare areas the framerate dips
Freeze after a couple of checkpoint loads in each run. Freeze before the final cutscene

Final credits video crashed the game. after the final fight the game shows static noise screen that you need to skip fast or the game will crash.
no tinkring needed, unless you want to limit TDB. final credits is broken and you need to skip or repeat the mission.
Changed Proton version to 5.13-6 before final mission and removed compatdata for Rustler.
On default Proton or Proton-GE after beating final mission, screen goes dark and it exits the game.
You can play on default Proton or Proton-GE without any issues but for the last mission, change the version to 5.13-6 and clear compatdata. One user claimed that he finished whole game on 5.13-6 without any issues: https://steamcommunity.com/app/844260/discussions/0/3115898713372567768/?ctp=12
The game crashes every few minutes.
Unity crash screen all the time in multiple games and with Rustler is not different. Another reason to avoid Unity games.
I tried Experimental, GE and other proton people mentioned here. I did not have these problems when I played the demo before release.
Too much crashing to be a good experience. The game is fun but the devs need to support us or it's not worth it.
-high
5.13-6 only works if game is set to full screen (launch game, change to full screen, quit and change proton). Proton 6.3-8 and 7.0-4 both work, but with those the game crashes about every other loading screen. This game HATES loading screens, so save often. Using -high in steam launch options has made no difference, and none of the GE proton versions help either.
5.13-6 only works if game is set to full screen (launch game, change to full screen, quit and change proton). This is the most stable proton version to use. I was not even able to launch the game with 5.13-6 before changing to full screen and retrying.
5.13-6 is the most stable proton version to use with the game. Proton 6.3-8 and 7.0-4 both work, but with those the game crashes about every other loading screen. This game HATES loading screens, so save often. Using -high in steam launch options has made no difference, and none of the GE proton versions help either.
You CAN play this, but it's somewhat annoying. Get it on sale if you're still determined you want to play this game.
Graphical glitches on video cutscenes
When changing the resolution you need to restart the game, otherwise it doesn't adjust automatically.
If you use "continue" option instead of loading the save directly, it looks like two game instances are running, making it unplayable and definitely not "Steam Deck verified" status worthy.
Crashes every 2h
All of the mentioned in particular point's, amount of bugs is significant and not worthy "Steam Deck verified" status at this stage.
The game crashes when you look at it. The game crashes when you move the mouse. The game just doesn't know what it wants.
Regardless of chosen Proton version, the game crashes at different points or different actions.
Lots of stuttering
Crashes a lot
Tried Proton experimental, 6.3-8 and 5.13-6. Experimental and 6.3-8 are very unstable.
Intro videos play with graphic glitches
Works great if using Proton 5.13.6, if using another version, expect constant crashes to desktop
Does not crash if forcing proton 5.13.6
The game is very playable under Proton 6.3-8 and running around 100 FPS.
Tested on Proton-6.21-GE-2 and Proton-7.1-GE-2 but the game would crash instantly after pressing New Game on both runner versions. The most stable and playable version is Proton 6.3-8. Running the game through Proton 6.3-8 stopped the game from crashing.
Required proton 5.0
It's crashing all the time. The longest time I could play without a crash is maybe 3 minutes.
Proton 5.13.6 no isue with sound or gameplay :)

Without audio, the game feels empty
Audio was working fine, but if you get a horse, it disappears completely

Too many crashes to let it be enjoyable.
Crashes qzuite often. Also in STeam reviews mentioned that the game is buggy. So could be possible that the crashes are general game issues.
Flawless
Anything other than the UI is completely black, including your character.
UI displays fine, but the rest of the screen is completely black.
Work perfectly with proton 5.13-6
No issue with proton 5.13-6. Crash with 5.21-GE-1 and 6.1-GE-2
Classic GTA vs Monty Python humor .. yeah this rules! Extremely playable. Bit heavier then expected.
Works perfectly out of box in Steam.

Runs really well out of the Box
I played the free demo version