kobo ereader

Hello, I think all kobo devices are non-free, however depending on the one you have you can use this https://github.com/lgeek/okreader

I use it on a kobo mini that I bought a long time ago, it works very nice, indeed much better than the original one in terms of performance and you can use bigger SD cards, but it is alpha software so some care is necessary. Anyway, the problem here is the proprietary firmware for the wifi, which I believe you can completely remove if you build the image yourself.

Here is a list of possible freedom issues https://github.com/lgeek/okreader/issues/9 unfortunately this question went unanswered. I think for eink devices (in fact for ebook readers, not considering tablets) this is the best option you have for any device.