Source? As far as I know they didn’t claim to not know location until iOS 17 release. Up until then they could access that info, and were required to give it up provided with warrants. This has been a reason Apple has actively been limiting the data they have access to. They cannot be compelled to give up data they have no way of accessing.
They do outline all of that, explaining how it works. The private key pair and secret are never sent to Apple. And yes, it’s end-to-end encrypted of course.
https://help.apple.com/pdf/security/en_US/apple-platform-security-guide.pdf
Page 202 of you care to learn how it works.
On top of being privacy focused themselves, they are only working with AI parters who also pass a third party code review verifying that zero user data is stored.
Shit on Apple for not being repairable, sure. Shit on Apple for their walled garden, sure. But shitting on Apple over privacy is insane. They are they only big tech company that actually cares.
Here is the documentation regarding third party verification of their security claims.
https://support.apple.com/en-ca/guide/certifications/apc3cea61877b/web
I’m assuming for some reason this is not good enough for you?
iCloud Keychain is super easy to use, but obviously you need a iOS/macOS to take advantage.