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The War on Passwords Is One Step Closer to Being Over
(www.wired.com)
This is a most excellent place for technology news and articles.
While the defaults are typically to use what the browser or OS has for storage and sync of the passkeys, you can use other things.
Like KeePassXC:
https://keepassxc.org/blog/2024-03-10-2.7.7-released/
As for attestation to how the key is stored securely (like in a hardware key), Apple's implementation doesn't support it for iCloud ones, so any site that tries to require it wouldn't work for millions of people. That pretty much kills it except for managed environments (such as when a company provides a hardware key and wants to make sure that's the only thing that's used).