There is also the Xteink4[0] that can be purchased on Aliexpress. It's just an ESP32 with an e-ink screen.

It costs more and is smaller but when you are done playing around with it you can flash it with Crosspoint[1], carry it in your pocket and read books on an e-ink display wherever you are.

[0] - https://www.youtube.com/watch?v=yMoq17-1pJA [1] - https://github.com/crosspoint-reader/crosspoint-reader