GIF dithering effect?

Anyone knows of a dithering effect that can reproduce traditional GIF dithers? Effectively, a way to make something look like a GIF, the more lofi the better.

Particularly I’d love an ISF version of the legacy Photoshop Export tool, where you can adjust palette, dithering algorithms, dithering amount, both for image and for masking and really grit the GIF down.

I’ve been using a mixture of Pixellate, Posterize, Dither-Bayer and various halftone effects to kind of fake it. I can handle some of the steps with builtin ISFs, but I think the dithering between colors is the missing link for nailing it. In some use cases dither-bayer can pass, but it’s obviously not a GIF when layered with proper GIF assets.

(If anyone has the technical know-how and think they could program it from scratch, I’d be happy to commission this!)

Here’s the legacy Photoshop dialogue and the results