
Game runs good out of the box.
You can run through the entire game without any crashes albeit the performance itself seems to be kinda wonky, have no clue if it's Proton or just the actual game. Others have said DX12 is better, but I didn't test it.
RADV_PERFTEST=gpl gamemoderun %command%

Works great out of the box
Set launch option PROTON_ENABLE_NVAPI=1 to enable DLSS
Works perfectly fine

I've completed the main story using Proton 8.0-5 . There are performance problems, but I'm not sure they are Proton related.
It has some performance issues with DX11 (mostly when using the flying saucer). DX12 seems more stable. Not sure if it's a Proton or a game optimization problem since I have no Windows to compare with.
Runs perfectly
Game crashed 2 times.
The game seems to perform slighly better in dx12 mode.
works perfectly as expected.

Game would sometimes crash after ~3hr of gameplay. Crashes only occured during loading sequences, so no progress was ever lost.
In the 'Properties > Compatibility' options it did not require setting any specific Proton. Game was installed vanilla and without any commands or mods. I did not attempt multiplayer or starting the game in DX12 mode. Runs very well overall.
gamemoderun OPENSSL_ia32cap=~0x20000000 DXVK_ASYNC=1 %command%
The game is largely performant and playable. Stay out of the skins menus! Reload from the main menu to fix any mission bugs
gamemoderun PROTON_HIDE_NVIDIA_GPU=0 PROTON_ENABLE_NVAPI=1 %command%
Some pop-in occasionally. The DX12 version of the game (selected when starting through Steam) is much more playable. The non-DX12 option is extremely slow and has severe pop-in issues
The game will drop from ~80FPS to 10FPS or less when viewing the Nav menu, saucer skin menu, or Crypto skin menu. Usually after exiting the skin menus, the framerate will stay stuck at 15-20FPS and required reloading from the main menu. Sometimes when starting a conversation with an NPC, there will be significant hitching/slowness throughout the scene
I have had the game freeze and crash twice in my 22 hours of playtime
If you played the first game on linux, this game would be just as fun, if not better.
The shaders and loading new assets causes slight performance problems here and there but in all, its still running really well.
Runs really well, I completed the first game in its entirety, and this game I assumed would run the same, and it does so far.
reduced TDP to 7
Crashed once in a three hour session
artifcats when using fsr
DX12 runs very poorly
I experienced light stuttering in the first cutscene and then heavy stuttering on the first mission rendering the game unplayable.
Experienced heavy stuttering during the first cutscene and intro mission - reduced all settings to low and stuttering was still extremely noticeable.
I experienced an issue where a cutscene was cropped in half - unsure if this is a compatibility issue or the game itself though.
gamemoderun %command%
Just had my first crash, going by the first game I'd assume there will be more; but I doubt many.
Note: Without Proton GE or gamemode I experienced stuttering. This is just my experience, I would always recommend people start with no tweaks to the game to gauge what tweaks they need.

Gira a 30-40 fps a impostazioni ultra e FSR1.0 impostato a "ultra quality" dalle impostazioni di gioco, che considerata la potenza di Steam Deck è già un ottimo risultato

Runs at 30-40 fps on ultra settings and FSR 1.0 set to ultra quality (from game's settings), wich is pretty good for the Deck