It feels like it's multishot nl-means, then immedeately those pre-trained "AI upscale" things like Topaz with nothing in between. Like, if I have 500 shots from a single session and I would like to pile the data together to remove noise and increase detail, preferably starting from the raw data, then - nothing? Only guys doing something like that are astrophotographers, but their tools are .. specific.

But for "normal" photography, it is either pre-trained ML, pulling external data in, or something "dumb" like anisotrophic blurring.