Knowledge Base Article for CERN Phonebook Application Support: Nick name and preferred last name in the CERN Phonebook: How can I change it?
Error message
Warning: cernoverride_preprocess_page(): Argument #2 ($form) must be passed by reference, value given in Drupal\Core\Theme\ThemeManager->render() (line 287 of core/lib/Drupal/Core/Theme/ThemeManager.php).