ok, I lied to you 😓, it's not about the partial refresh but about the 4 greyscale levels.
Discussion
the data sheet states that partial refresh is supported.
since I don't have the display, I can't do any testing
sorry Keith -> I will revise the description on github
The display I have is also listed as 4-tone grayscale.
It seems like a pixel mapping issue but I haven't dug deep enough to really understand how to alter the pixel order/alignment to whatever it's expecting.
I tried naively tweaking the `framebuf.MONO_*` constants but didn't get anywhere. Also flipping the `landscape` logic.
I would recommend to exchange the display, as fastest solution.