PSA: Important read if you're playing Rebirth on Linux (Bazzite/Cachyos/SteamDeckLike distros)

Hello there!

Since Rebirth is the new cool kid in town I figured I'll also post this tip on this subreddit for awareness.

If you are using a Linux distro that emulates the SteamDeck experience like CachyOS Handheld or Bazzite, you must know that Rebirth will load Steam Deck optimized hidden graphics settings even if you are playing on a powerful rig!

This fix will also apply to Legion Go, Bazzite users, and any users gaming on a Linux deck like distro, etc. Any powerful handheld users or using an egpu will definitely want to follow this!

I'm using cachyos handheld edition for a slick couch experience, where I can boot up my pc and use my controller in steam gaming mode. However, the SteamDeck=1 environment variable is passed to every game by default. Most games ignore this variable tho.

Rebirth being optimized for steam deck is using this hidden SteamDeck=1 variable to set some hidden settings you can't change manually and will result in MAJOR pop in and some weird graphical glitches even if you change all graphical settings to Ultra.
On my 5600x/6800xt, I had textures late loading and pop in everytime I moved my camera, I would see one ugly texture of environment for 0.5sec before the high res one.

How to know if you're affected? If on the initial launch Rebirth graphics settings were set to 1280x720p all low: you are running SteamDeck mode.

To fix this, you must :

1- Delete the compatdata rebirth folder at %steamfolder%/compatdata/2909400 (it's rebirth steam app id) You shouldn't loose your savefile if properly synced with steam cloud but make a backup first!
2- Open Rebirth properties in steam and enter this launch command (without quotation marks) "SteamDeck=0 %command%"
3- Launch Rebirth, it should compile shaders again or you didn't follow step 1 properly.
4- If you default to anything else than 720p low quality in graphics settings, you are done! No more ugly ass popin, games looks way prettier too.

If you are running Rebirth on a very low end hardware, you should probably use the steamdeck optimized settings but since we don't know all settings affected, you might try this to enjoy some graphical fidelity.

Enjoy!