Don’t throw away your Kindle, Jailbreak it and take back ownership. Make your Kindle even better with KoReader and other apps. If you wanna see whats possible i recomment this Yt video. If you wanna get started here are all instructions: https://kindlemodding.org/ Don’t let it scare you it seems complicated but its just a lot of (easy) steps. So definitely possible in <2h.
Where do you get books for the Kindle if not at Amazon?
I have an ancient Kindle Paperwhite that I love. Lately it has become very sluggish but still works and I have only bought books for it at Amazon. I’d love to correct that discrepancy.
I Personally use kobo but i have used Thalia or Hugendubel in the past aa well. I think you can use nearly every bookstore and transfer them with calibre. But sometimes you’ll get a asc(?) file instead of a epub and then use some software to “convert” it and maybe remove the drm