
gamemoderun %command%
I played the whole game in my system including the DLC missions and no issues.
I haven't tried native, after checking valve's recommanded runtime for steam deck at steamdb directly went for proton. I selected proton-ge out of habit.
Only minor issue, I can complain about is sometimes the mouse cursor image in the game gets stuck on any of the action related cursors and does not change until a mission is over/restart. That also might be a game's own bug though, not sure.

Proton GE for playing startup video. Proton better & stable than native also for possible changing to half refresh rate setting.
Used GE-Proton8-32 when playing but latest one should works better. Played this game exclusively on steam deck LCD docked 1080p with max settings from beginning till end (109.5 hours). I only got 45-50 fps without vsync or full refresh rate. I got 70 fps when choosing half refresh rate on game setting, my monitor refresh rate is 100HZ which i should be only got 50 fps but for some reason it lot smoother than that, it's stutter at first but i fixed it by turning off and on my monitor.
Game review : https://steamcommunity.com/id/not_Poland/recommended/610370/
2-3 crashes over my 41 hours of gaming, nothing to worry about.

I haven't encountered any issues with this one. I probably didn't touch any of the graphics settings, but I'm not 100% sure. In any case, here's what I used:
- Resolution: 1280x800
- Render scale: 100
- V-sync: Full refresh rate
- Quality: High
- Texture resolution: Full
- Shadows: High
- Shadow distance: High
- Anti-aliasing: On
- Water reflection: On
- Anisotropic filtering: High
- Ambient occlusion: High
- Viewcone quality: High
- Colorblind mode: Off

Perfektni hra
This is perfect Linux port. Everything runs butter smooth out of box!
Native game -> Works out of box
Xbox Wireless Gamepad was shown as Unknown Controller in-game and was not working. To fix it open game properties in Steam, then Controller -> Enable Steam Input
Tutorial Videos do not play
The game work out the box.
The game runs very well, at high framerate (on my hardware about 90fps stable).
When exiting the game i return to desktop normally, but the game stays in background with high cpu utilization, to exit correctly i have to finalize the game via steam menu.
I have to remove the start-up videos from game folder, these videos don't run, after removal i don't have any other problems in gameplay.

Works perfectly with this proton build: https://github.com/GloriousEggroll/proton-ge-custom
Proton-5.9-GE-3-ST GloriousEggroll
Proton-5.9-GE-3-ST

I used Proton-5.8-GE-2-MF

Not work on any version proton
- Official Proton 5.0-9
- Official Proton 5.0-9 with MF dll installed
- Proton-5.9-GE-2-MF
All these not work on my system. Only show up a small window(picture) then nothing happen, even no black screen.

ran a custom script as described by user class101
occasional crashes when reading tutorial messages
In order to get the game running in Proton, you have to use the following instructions (copied from another user below). Substitute the directory for yours if different.
Install GitHub: sudo apt-get install git
Download and install Microsoft Windows Media Foundation dll
cd /.steam/steam/steamapps/compatdata
git clone https://github.com/z0z0z/mf-install
cd ~/.steam/steam/steamapps/compatdata/mf-install
WINEPREFIX=/.steam/steam/steamapps/compatdata/610370/pfx ./mf-install.sh
I was able to view some tutorial objects but the game did eventually crash. Just ignore the tutorials and you'll be fine.

proton-ge-custom 5.9.GE.1.NR-2 GloriousEggroll
proton-ge-custom 5.9.GE.1.NR-2
can't interact with game after it loses focus
cloud game saves not working
Works fantastic. Played 25 hours with no problems yet.

Proton-5.8-GE-2-MF GloriousEggroll

Proton-5.9-GE-2-MF GloriousEggroll
Just Install latest Proton-5.9-GE-2-MF, works like a charm !
Black screen with mouse cursor after first game screen

Proton-5.9-GE-2-MF GloriousEggroll
nothing is clickable after alt tabbing out of the game
crashes after every mission
Showing Loader then black screen with cursor
Works great with both official Proton and custom Proton-GE but both methods have minor issues.
Official Proton
The steps below are required to install the Windows Media Fundation dll in your proton prefix, otherwise you might get a black screen after the Unity logo is shown.- cd ~/.steam/steam/steamapps/compatdata
- git clone https://github.com/z0z0z/mf-install
- cd ~/.steam/steam/steamapps/compatdata/mf-install
- WINEPREFIX=~/.steam/steam/steamapps/compatdata/610370/pfx ./mf-install.sh
Proton-5.9-GE-2-MF
This version is Windows Media Fundation dll ready so you do not need extra steps to install the dll.The issue with this method is that with Proton-5.9-GE-2-MF, when you ALT-TAB out of the game and go back in, nothing is clickable and you are forced to kill the process.
Switching from Official Proton to Proton-5.9-GE-2-MF
You might get a black screen upon launching the game because the steps you did to install the WMF dlls are in conflicts with Proton-GE so below are the steps to reset your proton prefix without loosing your saves- copy the Desperados III dir from ~/.steam/steam/steamapps/compatdata/610370/pfx/drive_c/users/steamuser/Local Settings/Application Data/Desperados III to a place of your choice
- delete ~/.steam/steam/steamapps/compatdata/610370
- in Steam verify game files of Desperados III
- restore your Desperados III saved directory in step 1 to the same location ~/.steam/steam/steamapps/compatdata/610370/pfx/drive_c/users/steamuser/Local Settings/Application Data/
I hope my experience with it will help you, enjoy this great game !
Works great with both official Proton and custom Proton-GE but both methods have minor issues.
Official Proton
The steps below are required to install the Windows Media Fundation dll in your proton prefix, otherwise you might get a black screen after the Unity logo is shown.- cd ~/.steam/steam/steamapps/compatdata
- git clone https://github.com/z0z0z/mf-install
- WINEPREFIX=~/.steam/steam/steamapps/compatdata/610370/pfx ./mf-install.sh
The issue with this method is that you might experience Unity crashes when viewing the tutorial objects starting from Chapter 1. Upon opening them, sometimes it works, sometimes it crashes.
Proton-5.9-GE-2-MF
This version is Windows Media Fundation dll ready so you do not need extra steps to install the dll.The issue with this method is that with Proton-5.9-GE-2-MF, when you ALT-TAB out of the game and go back in, nothing is clickable and you are forced to kill the process.

Not working with Proton 5.0-9, unity error shows up. Can anyone help me?
Maybe a graphic driver error, I am not able to update NVIDIA driver.
I am afraid I get a crash when launching the game with proton5.0-9. May anyone help me?

Games only starts with Media Foundation DLL, optional Tutorial tips will crash the game, otherwise works great!
Without Media Foundation DLL the main menu will not come up. Screen remains black after "Desperados III" logo
Game crashes when clicking on a tutorial tip note. The text of the note is displayed but the video does not load and the game crashes.
Starts with logo then black screen
The game starts and the logo is displayed. After that the screen turns black, although the mouse cursor remains active. Have to force quit after that.

Media Foundation DLL is required to run Desperados 3!
Game main menu does not come up without Media Foundation DLL and screen remains black after "Desperados III" logo
Starts and shows Unity and logo but then only get a black screen

You can't complete the game in this state.
The intro doesn't play, but just install windows media foundation resolved the problem. The game did crash on almost all tutorials, even mandatory ones. I therefore couldn't pass the first mission.

It works perfectly with this Proton version. With Protons available in Steam in default the game has problem after first loading.
5.9-ge-2-MF GloriousEggroll
Launches without issue. No problems experienced ingame. Maxed settings without any framerate issues or other bugs.
Proton-5.9-GE-2-MF GloriousEggroll

144 FPS buttersmooth gameplay.
use steam runtime on arch, not steam native due to an older version of a certain library being required.
- cd ~/.steam/steam/steamapps/compatdata
- git clone https://github.com/z0z0z/mf-install
- WINEPREFIX=~/.steam/steam/steamapps/compatdata/610370/pfx ./mf-install.sh
- cp ~/.steam/steam/steamapps/compatdata/610370/pfx/drive_c/windows/system32/mfplat.dll ~/.steam/steam/steamapps/common/Desperados III/