Unable to use non-default auth

[vaultah]

This page says

The default authentication type is set using defaultType: "form" Following types of the authentications are supported.

However, when I set defaultType: "oauth" and provide both oauth and form configuration like

authentication:
  defaultType: "oauth"
  oauth:
    issuer: "..."
    clientId: "..."
    clientSecret: "..."
    tokenEndpoint: "..."
    authorizationEndpoint: "..."
    jwkEndpoint: "..."
    redirectUrl: "..."
    redirectWebUrl: "..."
    userIdField: "..."
    scopes:
      - "..."
  form:
    selfSignKeyPair:
      privateKeyRsa: "..."
      publicKeyRsa: "..."

and open /trino-gateway, I can only see login/password form.

I suspect this is because /loginType returns { "code": 200, "msg": "Ok", "data": "form" }

so the form is rendered instead of a "Sign in with External Authentication" button.

Is this expected? Can I support both form/basic auth and oauth (by default)?