The author managed to double the framerate on GTX 1080.
FSR 2.0 Balanced with max settings
Modder PotatoOfDoom made a mod replacing Cyberpunk 2077's DLSS with FidelityFX Super Resolution 2.0. Both are upscaling technologies, but FSR 2.0 showed better results on the author's GTX 1080: the game now runs in 4K with about 45 FPS, which is twice better than the native 4K performance.
FSR 1.0 Balanced with max settings
PotatoOfDoom notes that DSLL works better than the 'hack', but the mod is meant for players with cards not supporting DLSS and adds some features absent in the native FSR 1.0. Note that this is a proof of concept that is still in development.
Earlier, AMD open sourced FSR 2.0, so expect to see more games and mods with the tech.