Frame generation went open source recently, as AMD added FSR 3 frame generation to its GPUOpen initiative, bringing competition to DLSS 3, locked exclusively to RTX 40-series GPUs. We've seen official FSR 3 support in a small amount of games so far, but the open source release has brought us DLSSG to FSR3 - a mod that works with any DLSS 3 frame generation title, swapping out Nvidia's solution for FSR 3. The upshot of this is that owners of Nvidia RTX 20 and 30 series cards now have their own frame generation solution. It's not perfect, there are issues, but fundamentally it works. On Nvidia cards, at least.
At least one other DLSS 3 to FSR 3 mod is coming which does work on AMD hardware, but right now, the first solution by 'Nukem', is exclusively for Nvidia users. That's down to the nature of the mod, which comes in two parts. First of all, you simply copy two DLL files into the game directory, then run a registry entry that fools your PC into thinking that your GPU is DLSS 3 compliant, even if it is not. Load up a game and the DLSS 3 frame generation option is no longer greyed out. However, toggling the option on activates the FSR 3 mod, not the original DLSS 3.
There are interesting side effects to this. Officially, FSR 3 only works with FSR 2 inputs. However, this mod allows you to use FSR 3 with any input you choose - so for a game like Marvel's Spider-Man: Miles Morales, you can add frame gen to FSR 2, XeSS, DLSS, Insomniac's ITGI or native resolution imagery. This is appropriate for owners of RTX cards, who stand to benefit from using DLSS spatial upscaling instead of FSR 2.