Kobo was on my short-list not long ago. They seemed like the most polished non-amazon option to me. I haven’t switched for now because my old kindle 2 is still clinging to life and because of it being long out of support from amazon I just keep it disconnected from the internet and sideload whatever I want.

With that said though, now that some decent kindle jailbreaking options are available, an old second hand kindle from eBay might actually be a very good option.