
Precisa forçar uma versão do Proton para jogar a versão Windows, que funciona melhor do que a nativa Linux. Pelo que li por aí, a versão Linux é basicamente a versão Windows com alguma compatibilidade aplicada, sendo que no Proton funciona melhor.

To have higher FPS than the capped 60
Native version kept crashing, but Proton works completely fine

The game has severe FPS problems. However, it can be ameliorated - not solved - by doing the following:
Navigate to Documents\My Games\Sanctum2\SanctumGame\Config\SanctumEngine.ini
set "bSmoothFrameRate" to FALSE
FPS is terrible, I have very good hardware and it remains < 60fps at all times, most of the time <30fps. However, I'm not 100% sure it's caused by Proton, as changing a config on the game files improved things.
I always use proton experimental, didn't even try standard version.

Some fps drop for the first few minutes after launching the game but stablizes afterwards
Do not use the native port
The Linux port of this game consistently crashes after a few minutes. Use proton.
Do not use the native port
The Linux port consistenty crashes after a few minutes in game. Use Proton
Worked great without any modifications.

It was not fun to play on the Steamdecek at all, controls where awkward and had fps drops on 2 of the 3 maps I tried.
Tried at both 40fps/40hz and also 60fps/60hz
First time with default controls I couldn't get the game started or move on the main menu. Then tried 2 community controls and I could get in game and play. All 3 control settings I tried on the steamdeck where not very good compared to when I played on PC (60 hours).
Some small performance issues on 2/3 maps I tried, mostly at the start
It technically runs, but I have no urge to play this on my Steamdeck which is sad because I love the game and was looking forward to playing a bunch of it on the deck. The controls where very frusterating and there was fps issues. It is working, but I am going to uninstall it as it just doesn't feel good to play on the Steamdeck for me
Seems to work pretty well. Maybe better than the native one.
Didn't properly go full screen until I alt tabbed out and in again.
Native version kept crashing instantly. Am still testing the proton one but it seems to be more stable and loads faster than the native one. Will make another report after doing more online testing.
Better than the native version, it has MSAA which the native version doesn't
Occasional fps drop

works out of the box
The native version crashed often. In contrast I'd no problems with proton so far.
Overall it runs really good. The short frame drops do not hinder the fun of the game
For me there are short dropouts from time to time.

The game worked out of the box on Proton. I did install additionally D9VK and it worked as well with it's DX9 to Vulkan translation.