Red Dead Redemption 2 didn't launch with support for AMD's new FSR 2.0 (FidelityFX Super Resolution) upscaling technology when it hit the PC, but modders quickly added FSR 2.0 support... and now, the developer has added official FSR 2.0 support into the game.

RDR2 update 1.31 adds AMD FSR 2.0 support, and more
The latest v1.31 update for Red Dead Redemption 2 on the PC adds support for AMD FSR 2.0, with developer Rockstar Games noting in the 1.31 patch notes: "AMD FidelityFX Super Resolution (FSR) 2.0 has been implemented". Ahhh, also... Rockstar, that would be "FidelityFX, not 'FidelityX' as you've noted here'.
You'll need to download the 433MB update, which will also add Reflex to reduce lag on the gamepad only (there's no help here for the mouse and keyboard input). Red Dead Redemption 2's new 1.31 update also sees Rockstar Games making improvements to Temporal Anti-Aliasing (TAA). So it's not just AMD FSR 2.0 in the new update, but that's the biggest deal here for sure. There's also plenty more in the patch notes, these three here are just the PC-only tweaks in the RDR2 patch.
Back in July 2022, we saw modder 'PotatoofDoom' -- the creator of the Cyberpunk 2077 FSR 2.0 mod -- pushing out a mod adding unofficial support for FSR 2.0 into Red Dead Redemption 2. It'll be interesting to see the performance between the FSR 2.0 performance between the mod and the now official FSR 2.0 support in Red Dead Redemption 2's new update.
As for FSR 2.0, I'll let AMD put it in their words: "AMD FidelityFX Super Resolution 2 (FSR 2) technology is our brand-new open source temporal upscaling solution. FSR 2 uses cutting-edge temporal algorithms to reconstruct fine geometric and texture detail, producing anti-aliased output from aliased input".
"FSR 2 technology has been developed from the ground up, and is the result of years of research from AMD. It has been designed to provide higher image quality compared to FSR 1, our original open source spatial upscaling solution launched in June 2021. Note that FSR 1 can still be exposed as its own upscaling option in addition to FSR 2 in game titles. Both technologies have different characteristics which may be suitable for a wider range of platforms and user preferences. For example, our FSR 2 partner title DEATHLOOP exposes both!"