[hkpack]

> They'll let you setup a passkey but then offer to let you sign in with a password first.

I am not sure if that is what you're talking about, but the standard way to implement login with passkeys is to use a normal username/password form and leverage the auto-fill mechanism to offer you to sign with a passkey if it is discoverable.

Another way is to have a two-step login, where you enter your login/email in the first step, and then use passkey to login in the next.

There are benefits and drawbacks in both of them.

Also, passkey can be used with multiple authenticators (like Yubikey), and most popular websites consider that verification of the user is not implemented sufficiently for some of them to be used as the only way of authentication, so they don't allow you to login with them without a second factor (i.e. password).