Trouble sending redirect after logout
To resolve current issue we need to create RouteSubscriber
my_custom/src/EventSubscriber/MyCustomRouteSubscriber.php :

&lt;?php

namespace Drupal\my_custom\EventSubscriber;

use Drupal\Core\Routing\RouteSubscriberBase;
use Drupal\Core\Routing\RoutingEvents;
use Symfony\Component\Routing\RouteCollection;

    /**
     * MyCustom Route subscriber.
     */
    class MyCustomRouteSubscriber extends RouteSubscriberBase {

      /**
       * {@inheritdoc}
       */
      public static function getSubscribedEvents() {
        $events = parent::getSubscribedEvents();
        $events[RoutingEvents::ALTER] = ['onAlterRoutes', -300];
        return $events;
      }

      /**
       * {@inheritdoc}
       */
      protected function alterRoutes(RouteCollection $collection) {
        if ($route = $collection-&gt;get('user.logout')) {
          $route-&gt;setDefaults([
            '_controller' =&gt; '\Drupal\my_custom\Controller\MyCustomUserLogoutController::logout',
          ]);
        }
      }

    }


Then add entry into my_custom.services.yml:

  my_custom.route_subscriber:
    class: Drupal\my_custom\EventSubscriber\MyCustomRouteSubscriber
    tags:
      - { name: event_subscriber }


Then create actual controller which will replace users module logout method.
my_custom/src/Controller/MyCustomUserLogoutController.php

&lt;?php

namespace Drupal\my_custom\Controller;

use Drupal\Core\Controller\ControllerBase;
use Drupal\Core\Routing\TrustedRedirectResponse;

/**
 * Class MyCustomUserLogoutController.
 */
class MyCustomUserLogoutController extends ControllerBase {

  /**
   * Logs the current user out.
   *
   * @return \Symfony\Component\HttpFoundation\RedirectResponse
   *   A redirection to home page.
   */
  public function logout() {
    user_logout();
    $logout_url = 'https://google.com'
    return new TrustedRedirectResponse($logout_url);
  }

}


Hope it will save your time.

Thanks