I've used this on a very old kindle. I had a kindle voyage from 2014 and installed this, it gave my kindle new life I didn't know was possible. It was fast and it had all the modern software features I would want.<p>Suddenly I found myself being able to organise my library how I wanted (through the use of folders, like any directory). Very easy to manage.<p>Also it made it super easy to send books without having to rely on the cable.<p>Ultimately, it was the hardware of the device that made me look for an alternative. I just couldn't stand micro USB charging in 2023. So I bought a Kobo and later on a palma (for the form factor).<p>Being able to install Koreader has now become a feature I select for. Also, it's very easy to sync books in Koreader, if your device is always online you can do it automatically or the way I do it is with some swipe gestures to push and pull the progress.
I'm a daily user on an android phone, as it's the only FOSS eBook reader still being maintained that has a feature set that includes white text on black background. It's pretty good, though it has some bugs, every so often an update breaks things and a new update fixing them is released soon, so I avoid updating if my version works fine for me. And since it's aimed at e ink readers it's UI is a little clunky for a regular mobile device. Great reader, renders everything you can think of, although every now and then with specific books it can get a little buggy. I haven't looked into the bugs to file reports.