Far Cry 5 does not officially support NVIDIA DLSS. However, modders have created ways to force DLSS via DLL swapping or using Universal Unreal Engine DLSS wrappers (even though FC5 uses the Dunia Engine).
Always save a copy of your FarCry5.exe and bin folder. far cry 5 dlss mod link
You cannot add modern DLSS to FC5.
If you have an RTX 20 or 30 series card and want to use Frame Generation (originally exclusive to the 40 series), you can use the mod. This replaces Nvidia's Frame Gen with AMD’s version, providing a significant FPS boost in compatible environments. Download dlssg-to-fsr3 on GitHub Far Cry 5 does not officially support NVIDIA DLSS