


Limited internal framerate to 30.
Fullscreen resolution needs to be manually switched to desired resolution if switching to playing the game on a PC with a lower resolution (that includes the Steam Deck).
Otherwise, you get the same issue "Raymond Racing" noted.
Native build cannot detect any controllers. This issue does not exist on the Proton build.
Mentioned in the "Fullscreen" issue.
It doesn't automatically detect resolutions across syncing the saves between different PCs. You need to change it manually before you switch systems, or you'll get the same bug.
Keep in mind, only a dozen people in total play this game online these days. Even though it's great.
As noted by previous user Raymond Racing, Linux build is fundamentally broken, and there's a very annoying bug if you don't switch the resolutions if you plan on playing the game on a system with a different resolution.
Other than that. The game's near perfect on the Deck. You can max it out, and set the internal framerate to 30. It's a very underrated little gem.

Due to the graphical and control issues I've described, you will get a bare ones, low-visual quality gameplay experience via Proton.
Main & Pause Menu screens force into an unknown horizontal letterbox resolution that makes tooltips & other menu text illegible.
Full screen was stuck in an awkward horizontal letterbox resolution for menus while live gameplay was in a 4:3 resolution with HUD elements stuck in the letterbox resolution size & placement
Y-axis inputs on the left analog stick & d-pad, and when using the left trackpad as an alternative, did not respond, making navigating the frontend, options & pause menus impossible to navigate. X-axis inputs worked fine however so the game can still be played, but only via the main Offroad Masters Campaign
Using Valve's native runtimes means DLC is not recognised and thus files do not sync with DLC saves if not playing via Proton

Some graphic settings are resource hogs, but with them disabled, can stay at a pretty steady 60 FPS
Anti-aliasing off or FXAA on low displays sparkling artifacting (common with low spec Unreal 4 games.) Using FXAA high or either Temporal AA fixed it with little performance change.
Couldn't go full screen as 1280x800 kept game widescreen; cutting off HUD, 1280x720 fixes it but is displayed normally in widescreen
Cutscenes (mainly company logos) are unsupported and show colored bars
100% recommend no shadow or reflection quality, as disabling both gives an extra 20 FPS. Ambient occlusion is only impacted minorly during night races with opponent's lights behind you. Everything else set to ultra or the highest settings works beautifully.

Used unofficial community controller settings works fine with that
Unplayable at default settings
This is a fun game and I'm enjoying playing it.
It would seem as though Codemasters were inspired by this game for their DiRT 5 release, however I'd recommend DiRT 5 over this. DiRT 5 is far better optimised and works perfectly on Deck without modifications.
Once this game has been twidled and tweaked then it can be played with fine however.
Added sharpening effect as described here https://steamcommunity.com/sharedfiles/filedetails/?id=1315184054
40Hz
Occasionally freezes for up to a second during gameplay
with mixed graphics settings, the game can run locked at 40 FPS with very minor dips in some levels

In-game 30 FPS cap. Medium graphics preset. The Deck is capable of locked 40 FPS at the Medium preset, but with minimal battery life.
Mostly okay. Some small text is hard to see when positioned over a lighter background.
Some shader compilation stuttering early on, rarely after the first 10 minutes or so.
Since Linux and Windows game profiles are separate, I did not test the native version, so I could continue my Windows-based profile.
In-game videos do not play with vanilla Proton. GE required.