Starfield was primarily written to feature AMD's FSR support, which is not surprising since the major consoles all use AMD processors and GPUs. Nowever, a few Nvidia fanboys were having major sulks at having to wait and were venting their collective spleens all over the world wide wibble.

Apparently, it was a terrible thing when Bethesda announced an official Starfield partnership with AMD this summer, and even worse when the game would not play nice with all Nvidia's bells and whistles because of that.

However, an enterprising modder created a mod that enables players with Nvidia cards to enable DLSS. The mod makes DLSS2 (ca. 2020) available for free. Modders have created another verson for DLSS3 (which adds the ability to use AI to generate frames in-between) but this is behind a Patreon paywall. This has lead to several other people to crack the DRM protecting the mod. 

Arstechnica points out that few Nvidia card users would spot the difference anyway. In its testing on a GTX 2080 Ti gaming rig (running at 2560×1440 resolution, Ultra quality, and 50 percent render resolution), it hit 35 frames per second using both the DLSS mod and the game's built-in AMD FSR2 support (which also works on Nvidia cards). Neither upscaling technology had an apparent performance edge, even as both improved significantly on the ~25 fps frame rate when running at full resolution without any upscaling (and even as DLSS has shown superior visual quality in other tests).