I have found recently that one special version of e-ink kindle has a firmware seems like using FireOS with u-boot
The product:
https://www.amazon.cn/dp/B01I235KH4/ref=fs_kindlemigu
The firmware:
https://s3.amazonaws.com/firmwaredow...gu_5.7.2.1.bin
The source code:
https://s3.amazonaws.com/firmwaredow...171121.tar.bz2
I think the person's software is based on this firmware.