ExampleController.php

<?php

public function runTask($task_id, $site_name) {
    $plugin = $this->pluginManagerService->createInstance($task_id);
    $site = Site::load($site_name);
  
    $status = $plugin->run($site);

    if ($status == 'Success') {
      $output = $plugin->getTaskOutput();
    } else {
      $output = [
        '#type' => 'html_tag',
        '#tag' => 'span',
        '#attributes' => [
          'class' => ['error'],
        ],
        '#value' => $this->t('Task failed'),
      ];
    }

    $response = new AjaxResponse();
    $response->addCommand(new HtmlCommand(
                          ".details-display[site='" . $site->getName() . "']",
                          $output));
    return $response;
}