Again, do all major sites allow you to register 6-10 passkeys? Not asking if they could in principle, but do they in practice do it? And how easy is it to log in with a new device to generate that passkey? Do I have to jump through hoops on my laptop, second phone, secondary browser, and so on?

Finally, if it is easy to register a new device, how does the anti-phishing still work? Can't an attacker just convince me to use whatever means I would normally use to register a new device, instead of an existing secure passkey?