This is related to https://gitlab.com/mailman/postorius/-/issues/590 The bug is actually in django-mailman3. The file https://gitlab.com/mailman/django-mailman3/-/blob/master/django_mailman3/templates/openid/login.html?ref_type=heads is openid/base.html, which extends socialaccount/base_entrance.html But it should also extend the django_mailman3/profile/base.html for the styling to be present.