Entity reference view display is not displaying fields as expected
You could use the realname module (which now has a D8 release). Or, you could alter the user name as displayed in Drupal:

function HOOK_user_format_name_alter(&amp;$name, $account) {
  // Load the full user account.
  $account = \Drupal\user\Entity\User::load($account-&gt;id());
  // Get the full name from field_name.
  $full_name = $account-&gt;get('field_name')-&gt;value;
  // If there's a value, set it as the new $name.
  if (!empty($full_name)) {
    $name = $full_name;
  }
}