
I think it has native deck support now and you might not need proton. You will need proton if you weant to install mods though.
I installed Session Mod Loader
Can be hard to read on the deck screen but if you've played the game already you should be fine.
Highly recommend installing the Session Mod Loader for more maps, clothes, decks, etc. It's very easy to install, just make sure you download Version 3.0.5 from the github as that is the latest one that will work on deck. Once installed, add the .exe to your steam library and force it to use proton. Do the same for the Unreal Mod Unlocker and you're good to go. Do not launch the game from the Mod Manager though. It doesn't seem to work for me but launching through steam after adding my mods works fine.

Все в порядке
Присутствовали небольшие дропы фпс, по совету ниже отключил вертикальную синхронизацию и их стало ощутимо меньше
Играбельно, геймпад ловит без проблем, с производительностью ничего критичного нет. Работает, считай, из коробки.
Works OOTB, no issues, just click play with proton 9 or you can add mangohud also to your launch command

Runs OOTB for me, without any bugs or artifacts.
Great experience so far, haven't had any problems whatsoever.

If Display is set to Fullscreen the image is streched and weird, must set it to Windowed
I tried to follow the tips from others here but kept having issues. What worked for me is a bit different. Steam FSR must be off or the performance dip will make it unplayable (20fps). On the Steam side, I set: Disable Frame Limit: on; Allow Tearing: on; Half Rate Shading: on; (didn't experiment with TDP and GPU clock yet). On the Game options: Window mode must be Windowed, you'll have to play a bit untill you are able to open the options menu; Resolution is native, 1280x800; frame rate is 60fps; AMD FSR in Ultra Quality; Everything else is on high and Vsync is On; I've been playing it on the PS4 and here to compare and with these settings the Steam Deck feels prettier and more responsive, with a stable 60fps. Enjoy!

Does not work with Pipewire.
Instantly crashes on startup, once switched back to Pulseaudio it works flawlessly.

No major problems, everything works just the same as playing on Windows. All experimental features are working as intended.
Very minor frame drops for a few seconds, then goes back to normal - disabling Vsync fixed this.
Works greate of out the box without any tinkering
Works out of the box

Stable 60FPS Settings! Steam Deck's Native FSR: Enabled, Sharpness at 5 Window Mode: Full Screen Resolution: 1152 x 720 AMD FSR: OFF Resolution Scale: -4 from max Shadow Quality: Low Anti-Aliasing: High Textures: Medium Effects: Low Post Processing: High Vsync: Off (Steam Deck natively already has Vsync so you don't need to enable it) Brightness: Default
Game initially boots up in a really weird resolution

Using proton experimental I have had zero issues with the game. Very satifying experience so far.
Ive had to do nothing extra to play this game without issue.

Session and many other games I have do not run on Nvidia driver 535. You may need to downgrade to 525.
No problems

Unenjoyable due to input delay. Fixes tried: Max cloud coverage, 1080/720 resolution, med graphics, day/night cycle off. PS1 era graphx tho.
While attempting to dock or use external displays, I encountered a significant amount of lag that rendered the game highly unpleasant and kind of unplayable. A delay of approximately 1 to 2 seconds was consistently present.
Cryo Utilities used
I used Cryo Utilities way before installing this game but I don't really think it has changed the performance of it. There is a little lag spike when loading into the game for the first but other than that it runs a smooth 60 FPS no FSR. Max temp I saw was 80c on both CPU and GPU.
As good as native on my system!
Runs the same as on windows 11. Didn't have to do anything extra to get it running.
In game i set all the display settings to medium but turned resolution all the way up. It runs very smoothly!
It works as well as the current state of the game allows it to work. Framerate issues are no worse than the Windows experience.
Infrequent "Fatal Error" while game is starting, but restarts OK. Twice in a month since v1.0. Unable to replicate reliably.
The game is still in need of optimisation. Some maps get a solid 60fps (underground car park), some maps tank to 25-30fps (areas of SFC). Most manage around 45. After much tinkering with in-game settings I've found high settings, 45fps cap (deck uncapped) and v-sync off gives the most consistent performance. Also, and ymmv, I've found that disabling day/night cycle, setting sun angle to max, cloud cover to max has helped with consistency by minimising shadow contrast.
The 1.0 release notably improved performance. On 40hz it runs perfectly stable on mid settings 800p. Drawing about 16W. Definitely improved!
Performance definitely increased after the 1.0 update!
It just works
It's as simple as it gets. You download and install the game and it plays perfectly fine.
Adjusted settings to lowest
When turning settings to low the game gets very dark, not normal
Performance is very slow even on the lowest settings. Running the game using Windows performs much better
Game runs great if you don't mind 35-45 fps on high graphics settings. Didn't try lower settings since I don't really care, it runs great.
Runs great if you don't mind 35-45 fps.
Seems fine
It's still only hitting 30 - 40FPs, but the input lag can be disabled by setting the fps limiter from gamescope to unlimited and limiting the fps ingame + turning vsync off. Still not as good as 60fps but much better.
Not yet at 60fps, still fun
Some models had default textures. Turning the "effects" option down resulted in VERY DARK lighting, too dark to play.
Game runs between 30 and 45 FPS after turning most options down to low and rendering at 540p with FSR. Limiting to 30 made the game feel choppy. 45 drew the whole 25W and wasn't that smooth neither. Playable but not smooth.
Playable but not enjoyable (yet).
Works perfectly
Using ps4 controller, everything seems to be working great.
Crashes right after launch
the game launches into the main menu aund crashes after a few seconds. When i'm fast enough i can create a character but it fails to load into the map and my system hang up.

works great, runs like a native game, everything on ultra no issues.
in character selection the OG dreadlocked guys face is pixelated

(Reported experimental version: Proton Experimental)
https://www.protondb.com/app/861650#77xXmDc4EW
Replaced "UE4PrereqSetup_x64.exe" as per review below.
Light flickering very rarely but still completely playable.
Game only managed to launch on Proton Experimental, Dualshock4 works fine. Perfectly playable experience.
On the initial screen showing the skater standing there the light coming from the sun is flickering like a strobe light. Once you start the game it's fine though.

Prompted me to install Microsoft Visual C++ Runtime and UE4 Prereqisites which failed with "invalid ACL" error. But Christophrhein's solution for Medieval Dynasty works for Session too:
Download https://aka.ms/vs/16/release/vc_redist.x64.exe
Copy vc_redist.x64.exe into .steam/steam/steamapps/common/Session/Engine/Extras/Redist/en-us/
Rename vc_redist.x64.exe to UE4PrereqSetup_x64.exe (overwriting or rename the existing file)
Will not start with an error of Microsoft Visual C++ Runtime is not installed

Installs but then fails to launch.
Installs but then fails to launch. Always prompts that it needs "Microsoft Visual C++ Runtime", then launches a UE4 dialog that eventually errors.
Worked perfectly with Proton 5.0-10
Performance was pretty good, on Windows I used to get around 80fps in EPIC configuration, here I get 60 stable, 100% playable
Runs smooth, just like in windows
runs fine
can crash if u change resolutions too often
runs a little bit slower than windows but is expected given my hardware
Issues were subtle enough for me to miss for a couple days. Very playable and loads of fun
when you fall off your board, the board impact sound effects will loop until you respawn (so don't touch the replay editor until your character respawns). rarely noticeable because I usually respawn before it plays the sound again, but it's sometimes annoying when I open the replay editor out of habit immediately after falling.
occasional texture pop-in for certain decorative decals. looks to be some view distance or culling issue. not sure if this exists when playing natively on Windows. rarely happens, so it isn't experience-breaking
My brand new Arch install was getting ~15fps (it used to get well above 60 with absolutely no tweaks on Manjaro) until I used KSysGuard to set the CPU and hard disk priority to max. Game runs perfectly after setting priority