Did you look at grimmory

What about grimmory

Because my e-reader only runs koreader

Does it support epub?

Too complex

UI IS TRASH AND OUTDATED

Janky and doesn’t look nice

Yes but there are lots of plugins and tweaks from being able to get Anki on there to chess clients. It is 100% possible just I am not clever enough to make it.

oh sorry, my first language is spanish, not english. I want to play lichess on it

Koreader is an e-reader software