Kobos let you install custom book-reading software without too much hassle. KOReader[0] is the most popular one. I like it because it allows for a ton of customization, can properly render pretty much any EPUB you throw at it (much better than stock), and can reflow PDFs (using K2pdfopt[1] under the hood). But there are some other alternatives, including Plato[2] (simple, easy to use, fewer features) and PBChess[3] (closed source, play chess on your Kobo).

The MobileRead forums[4] are quite active, you'll find a lot more there.

[0] https://github.com/koreader/koreader [1] https://www.willus.com/k2pdfopt/ [2] https://github.com/baskerville/plato [3] http://pbchess.vlasovsoft.net/en/ [4] https://www.mobileread.com/forums/forumdisplay.php?f=223

> I bought mine just because Kindle doesn't have ePub support[0].

> [0]I know about Calibre.

Amazon actually provides their own tool to produce a Kindle document from an ePub. The assumption seems to be that you'll naturally produce Kindle ebooks by writing ePubs and converting them. But the tool doesn't work!

I wanted to have line numbers floating to the left of the main text. ePubs are just HTML, and it's easy to do this. It works fine in ePub readers. But while I tried multiple different ways of accomplishing this in an ePub, none of them made it through the conversion to Kindle.

Alternative reader applications like koreader and plato open up more customization than the default reading app allows for.

https://github.com/koreader/koreader https://github.com/baskerville/plato

I have a Boox and i just drop the epubs on the sd card.