Ask HN: Clear, Open E-Reader?

I'm looking on the market for an ereader, one that is (reasonably) open and that lets me sideload epubs, ideally supporting Calibre. I have about 50 epubs of classic works that I'd like to read, sourced from Standard Ebooks and Project Gutenberg.

I'm willing to pay for something that has the following:

1. Clear screen (ideally close to the Kindle Paperwhite, but just clear in general)

2. Annotation support (either highlighting/notes, or both)

3. Some way to read articles (does this even still exist anymore?)

4. Sideloading, no full lock-in is a must. Willing to jailbreak if needed.

5. Reasonable page-turn speed (less than 1 second)

Are there e-readers that fit most of these?