https://api.drupal.org/api/drupal/core%21modules%21forum%21src%21ForumManager.php/8.9.x
ForumManager.php | Drupal API
phpdrupalapi
https://api.drupal.org/api/drupal/core%21modules%21forum%21src%21Controller%21ForumController.php/property/ForumController%3A%3AforumManager/9
ForumController::$forumManager | Drupal API
drupalapi
https://api.drupal.org/api/drupal/core%21modules%21forum%21src%21ForumManager.php/property/ForumManager%3A%3AlastPostData/10
ForumManager::$lastPostData | Drupal API
drupalapi