How do I sync books across devices?

I own a Boox Palma 2 and a Kindle Paperwhite 11, and I to sync reading progress and maybe even syncing reading stats across both of them.

Here's what I tried so far: I tried Syncery, but I don't know how to properly set it up. I was using BookFusion, but it stopped working (it only synced reading progress, not stats), I tried updating but it simply won't sync anymore, I tried pushing my reading progress but it always fail. BookFusion used to work wonders.

What else can I do? I don't want to always have to sync both manually like before.