What is that noise actually? It's clearly not JPEG artifacts. Is it dithering from converting from a higher bitdepth source? There do appear to be very subtle gradients.

I would bet it's from AI upscaling. The dark edges around high contrast borders, plus the pronounced and slightly off-colour antialised edges (especially visible on the right side of the J) remind me of upscaling models.

Not even the white is pure. There are at least #FFFFFD, #FFFFFB and #FEFEFE pixels sprinkled all over the #FFFFFF.