ElectroLisa

You can play the mod on any SteamVR compatible headset, including the very first HTC Vive, the Oculus Rift CV1 and many others. You don't need an Index to play it

Steam Deck runs an embedded session of Gamescope which uses DRM (no not copy protection) to display games.

Running Gamescope as a launch command will run it in a nested session, where it's output is being sent to your display manager, ex. Kwin. That's where the lag can happen, and usually does especially in GPU bound scenarios

Try passing SDL_VIDEODRIVER=x11 in launch parameters

Gamescope will add input lag which is something you don't want to have in a game like CS2

I guess this game is now officially Abandonware, shame to see Epic neglect their legacy and what made them popular for the first time.

BTW if you have the game on Steam you can use Luxtorpeda to automatically obtain the newest oldUnreal binary files for Linux

Issue not necessarily appearing on the Steam Deck but it would benefit from it as well - better handling of mixed input from a controller and mouse. I have a Steam Controller and prefer to have it simulate a controller in FPS games but to have the right touchpad work as a virtual mouse to ignore in-game acceleration curves and deadzones.

Some games handle it well, like Cyberpunk 2077, some games like Grounded tend to show keyboard prompts whenever it would detect mouse input but still function correctly. If I'm not mistaken Borderlands 2 would drop it's UI controller layout whenever a mouse input was detected, which can probably be skipped by using layout switching/overrides from Steam Input. The worst offender so far is Hunt Showdown, where the game freezes for 0.5 s when it detects mouse input, even if it's a physical mouse input.

All of my testing has been conducted on Linux, not sure how it behaves on Windows

Does it also affect SteamCMD?

It is mentioned on their roadmap

KDE Plasma, yes that happens when electron apps run in native Wayland mode

Except it also has said issue. Additionally it causes my VPN connection to drop when watching streams, and does noise cancellation despite that option being disabled.

Please bring back mini iPhones with Face ID

They're probably adding EA anti-cheat and that's why they say they're removing the Steam Deck support