I suggest buying M5Stack PaperMono instead. It's an esp32 board with an eink screen and a battery. I bet someone will make an open source firmware for it
Is that actually a product intended for consumers though? Looks more like a development board than a product for "normies", like the Xteink stuff.
M5 device are cool but they do have that, as ugly as it is useful, functional diagram printed on the back...