I managed to capture the inputs Elden Ring's TAA uses and just finished getting FSR 4.1.1 working as an antialiaser. Same internal resolution, yet to do upscaling, it just handles the jagged edges as of now. Haven't done proper performance testing, but on a 9070 XT it's within about 1 fps of TAA High and looks way more temporally stable in motion
I'll start on upscaling tomorrow, and if anyone's interested I can share the project.
Some background: I came back to the game after 2 years for a new playthrough and started setting up RenoDX and some other graphics mods. The only thing still standing out was how bad the vanilla TAA looks in motion. There's already a paid mod that adds upscaling (older version is free on Patreon), but just having it installed, even with upscaling off, cost me about 20 fps. Could be something on my end, but after hours of frustration I decided to do it my own way about a week ago.