- Libby on Xteink: https://www.theverge.com/tech/976390/xteink-x3-x4-x4-pro-e-r...

- There's KOReader sync in Crosspoint

But the biggest issue with Kindle is the vendor lock-in and the books don't even belong to you. There were many cases of Amazon deleting books with no refunds. That's why I am not getting any Kindle ever again.