As the article stated: "I want you to remember this quote and it's implications. Users should be able to use any device they choose without penalty."
As you've pointed out:
>> Backups: It depends. It seems like the big players (Google, Apple) are pushing an implementation where your passkeys are backed up either in the Google Password Manager or iCloud keychain. That way if you lose your device, you can recover your passkeys the same way you recover your other phone data.
and again:
>> Storage: It depends. Google and Apple are pushing phone implementations where passkeys are protected by a hardware security module of some sort, either the iOS keychain or Android Keystore. The private keys can't actually be stored in the HSM though, because you need to be able to back them up.
How can I get my passkeys and back them up on my own storage media? (e.g. USB drive, encrypted cloud storage, burn to a disc, etc.)
How can I import passkeys generated elsewhere?
If you cannot backup or import the passkeys, then you do not control them. They are not your passkeys--they belong to Google or Apple, etc.
And as the article states, in most cases these passkey providers do a piss poor job of managing their passkeys that they claim belong to you.