This is great! I've always wanted more hackable e-ink devices -- the Kindle is nice but it feels like there's so much unrealized potential of an e-ink screen.
The reMarkable is a pretty hackable eink device.
The RM1 was pretty well modded, but the RM2 is currently somewhat stuck due to a missing frame buffer driver. Some good people are working hard on it though and it seems like it’ll be solved fairly soon. [0]