I have built one by myself with a waveshare display. The dithering is visible and the contrast is bad. But from distance it is not noticeble.

I've done the same and I'd say that it didn't produce a great result. I did it for my father as a gift and while I liked the project because of the novelty of 7 color eInk tech, the image was low res, dithered, and tinted yellow. My father was grateful but he probably would've liked a normal LCD display lol