Something overwhelming of WebAuthn/U2F/FIDO2/Passkeys is that it has many different modes and settings [0]
So, my understanding is that you need to find the settings to 'upgrade' the modes from 2FA to a Passwordless alternative. Not all devices are supported.
I like this explanation in Ruby [1] [2] of all the process between the server and the browser. It also has an example you can try on your browser to see if your devices/OS are supported. Look at the bottom the distinction between Passwordless and 2FA.
I'm making a proof of concept of WebAuthn the only login option, for a toy project in PHP [0] with this library [1]
It has been an interesting exercise to understand the tricky parts of it.