Webauthn login WebUI

Hi I am attempting to configure privacy idea such that users can log into and manage their tokens over the webui. For this I have set up some simple policies. If a user has no tokens they are authenticated with the userstore credentials, otherwise their 2fa token is used.

Therefore the following policies are set:

authentication (passthru: userstore)
webui (login_mode: privacyIDEA)

Now the “username and password” fields function as a “username and token” field, which works fine for text based tokens. However, challenge response mechanisms like webauthn cannot be triggered by this. How can I make the login form request my webauthn token? Any help is greatly appreciated.