Why lower limit is 40fps/hz when you can go to 30fps/30hz ?

Try that : https://github.com/ryanrudolfoba/SteamDeck-RefreshRateUnlocker

I had this problem today : i just changed UMA buffer size to 4g and the game is now working in game mode

I’m using Xbplay : it work perfect on SteamOS ! You have a trial for 20 minutes for testing (and if you want to remove the trial, you have to pay 5.99$ only one time to have unlimited access)

I tried with Edge method but you still have black bars ( Xbplay no black bars with correct settings )

With Xbplay, u can even add the game from Xbox cloud directly into your Steam library

Don’t play games at 15w and it should be ok

No but you can increase your battery life with undervolt and playing at 30 fps (3h20 playing RDR2)