Enabling FSR 4 on GE-Proton under Bazzite Linux

TL;DR: In Silent Hill 2 or any other (non-Vulkan) game that supports FSR 3.1 add the following Steam launch options and be sure to select the latest GE-Proton PROTON_FSR4_UPGRADE=1 SteamDeck=0 %command%

The long story:

• make sure GE-Proton is installed and selected for the game in properties / compatibility. Under Bazzite I used Proton+ https://github.com/Vysp3r/ProtonPlus
• the game must support FSR 3.1 or the auto upgrade will not work
• Vulkan games like Doom: The Dark Ages are currently not supported for FSR 4 see https://github.com/optiscaler/OptiScaler/wiki/FSR4-Compatibility-List
• under properties and command line options add PROTON_FSR4_UPGRADE=1 %command%
• some games disable certain options (like Silent Hill 2) when under Proton/SteamOS and you must add SteamDeck=0 as well to be able to select FSR 3.1
• to verify that the upgrade worked, use the additional switch PROTON_FSR4_INDICATOR=1 that will add a text overlay to your game
• only RX 9000 cards (i.e. 9060 or 9070) support this method
• a hack exists for older cards

Links:

• FSR 4 Linux Setup: https://github.com/optiscaler/OptiScaler/wiki/FSR4-Compatibility-List#fsr4-linux-setup