I have no idea.
I do know that I'm not super enthusiastic about Amazon being the one controlling my reading history, but I've tried migrating to several of the alternatives and it's just too much.
Goodreads has a nice page where you can see 50 books at a time, skim down the list, and checkbox to make bulk changes. I'm willing to painstakingly reconstruct lists like that with an alternative, even though it will still be kind of a pain. But I'm not willing to manually search every title to add it to a list, or go through my reading history and need multiple clicks and backwards navigations for every book I want to add to a list, and that's the state of anything I tried a couple months ago. Bookwyrm specifically sounds really nice, as a way to use federated tools to find people with similar interest and follow their reading and share. But the transfer is a lot.