I’ve used Kobo and Ebooks.com, and import into my Calibre library. I know some authors have a way to purchase directly on their site.

It absolutely does. https://plugins.calibre-ebook.com/ there is a KFX input plugin. Also, if using an older version of kindle for PC you can batch download your whole library and import to Calibre.

Yeah, but when signal complies they give date you made your account and when you last accessed. And that’s it. Probably much less than the others give.

US specific and not sure for how much longer, but the courts have generally held that you can’t be forced to give up a password to a phone. It’s covered under the 5th (and 4th) amendments. That being said, most stock phones are vulnerable to cellubrite cracks.