Worth mentioning it's not limited to Android! It also runs on Kobos, Kindles, Pocketbooks, etc.

How does it runs in Kindles? Which ones are supported? I'm interested

Not personally familiar with the details, as I don't have any Amazon devices. Sounds like it involves jailbreaking and per-model differences: https://github.com/koreader/koreader/wiki/Installation-on-Ki...

Make sense now thanks

Ah, didn't know that.