If you have a Mozilla LDAP contributor account (i.e. an account you manage on https://login.mozilla.com), you may now register WebAuthN tokens in addition to DuoPush.
Note that you can register multiple tokens (this is recommended, in case you lose access to one), and mix WebAuthN security keys with other methods.
If you do not use such an account this does not apply to you. For example, if you use a GitHub account to login,GitHub already supports WebAuthN natively (they’re called Security Keys).
Want to know more about WebAuthN?
Here is a nice introduction: https://webauthn.guide/
Here is the MDN documentation to implement WebAuthN on your web pages: https://developer.mozilla.org/en-US/docs/Web/API/Web_Authentication_API