An interesting challenge… As LMP3D says, the appeal is mostly down to the selective simplification of different areas. There are almost no gradients, color dabs are quite uniform in tone and have distinct edges etcetera.
It would require a lot of experimenting, but recreating something like that would probably entail a combination of textures and postprocessing. Textures would need to be decidedly “painterly” themselves, with a limited palette, no smearing/gradients, quite geometric strokes with apparent brushwork. You could probably get ~75% there just by texturing alone.
For post, you’d be looking at something like quantizing perhaps (could be fairly easy to implement with a custom LUT) but ideally you would also want something similar to a “smart blur” and I have no idea how feasible that is, or, if possible, how expensive it would be in terms of processing. The perfect solution would maybe tank your framerate something fierce