name to preferred_username mapping not working

[FLAK-ZOSO]

I am trying to set up an OpenID Connector following the documentation. In particular, it is a sandbox MyAccessID connector. More about it here.

- type: oidc
  # https://dexidp.io/docs/connectors/oidc/
  id: myaccessid
  name: MyAccessID
  config:
    insecureSkipEmailVerified: true
    scopes:
    - openid
    - profile
    getUserInfo: true
    claimMapping:
      preferred_username: name
    overrideClaimMapping: true

I omitted the ID and token of the client on purpose, don't worry, they are there

It does not support the claim preferred_username, instead it supports name in the UserInfo endpoint, thus the mapping above.

However, in my logs I still get the following. I have no clue on what's happening to be fair.

Sep 02 13:55:08 controller0.flak.test ondemand-dex[1157933]: time=2025-09-02T13:55:08.460Z level=INFO msg="login successful" connector_id=myaccessid username="Mattia Marchese" preferred_username="" email=" (unverified)" groups=[]

Notice how preferred_username is empty

I don't know how to troubleshoot this... and logging is no more verbose than what you see there. And I have no clue on how to make the logging more verbose, having found no documentation on the topic; my best attempt was this, made out of thin LLM-air.

dex:
  logLevel: debug