对于那些想知道如何使用新的注销定制来实现外部重定向的人：
如documentation中所述，创建一个新的CustomLogoutListener类并将其添加到services.yml配置中。
CustomLogoutListener类应实现 onSymfonyComponentSecurityHttpEventLogoutEvent 方法，该方法将接收 LogoutEvent 作为参数，允许您设置响应：

namespace App\EventListener;

use JetBrains\PhpStorm\NoReturn;
use Symfony\Component\HttpFoundation\RedirectResponse;
use Symfony\Component\HttpFoundation\Response;
use Symfony\Component\Security\Http\Event\LogoutEvent;

class CustomLogoutListener
{
    /**
     * @param LogoutEvent $logoutEvent
     * @return void
     */
    #[NoReturn]
    public function onSymfonyComponentSecurityHttpEventLogoutEvent(LogoutEvent $logoutEvent): void
    {
        $logoutEvent->setResponse(new RedirectResponse('https://where-you-want-to-redirect.com', Response::HTTP_MOVED_PERMANENTLY));
    }
}

# config/services.yaml
services:
    # ...
    App\EventListener\CustomLogoutListener:
        tags:
            - name: 'kernel.event_listener'
              event: 'Symfony\Component\Security\Http\Event\LogoutEvent'
              dispatcher: security.event_dispatcher.main

SecurityController中的logout方法实际上不会被击中，因为Symfony将拦截请求。如果您需要在注销后执行某些操作，可以使用注销成功处理程序

namespace App\Logout;

use Symfony\Component\HttpFoundation\Request;
use Symfony\Component\HttpFoundation\Response;
use Symfony\Component\Security\Http\Logout\LogoutSuccessHandlerInterface;

class MyLogoutSuccessHandler implements LogoutSuccessHandlerInterface
{
    /**
     * {@inheritdoc}
     */
    public function onLogoutSuccess(Request $request)
    {
        // you can do anything here
        return new Response('logout successfully'); // or render a twig template here, it's up to you
    }
}

并且您可以将您的注销成功处理程序注册到security.yaml

firewalls:
    main:
        anonymous: lazy
        provider: app_user_provider
        guard:
            authenticators:
                - App\Security\LoginFormAuthenticator
        logout:
            path: logout
            success_handler: App\Logout\MyLogoutSuccessHandler # assume you have enable autoconfigure for servicess or you need to register the handler

多亏了Indra Gunawan，这个解决方案才奏效，我的目标是重定向到登录页面，并显示“您已成功注销”之类的消息。
在这种情况下，必须调整LogoutSuccessHandler以路由到登录页面：

namespace App\Logout;

use Symfony\Bundle\FrameworkBundle\Controller\AbstractController;
use Symfony\Component\HttpFoundation\Request;
use Symfony\Component\Security\Http\Logout\LogoutSuccessHandlerInterface;
use Symfony\Component\Routing\Generator\UrlGeneratorInterface;
use Symfony\Component\HttpFoundation\RedirectResponse;

class MyLogoutSuccessHandler extends AbstractController implements LogoutSuccessHandlerInterface
{

    private $urlGenerator;

    public function __construct(UrlGeneratorInterface $urlGenerator)
    {
        $this->urlGenerator = $urlGenerator;
    }

    public function onLogoutSuccess(Request $request)
    {
        return new RedirectResponse($this->urlGenerator->generate('login', ['logout' => 'success']));
    }
}

需要在routes.yaml中定义路由登录：

login:
    path: /login
    controller: App\Controller\SecurityController::login

logout:
    path: /logout
    methods: GET

在这种情况下，当注销时，您将被重定向到一个URL，如：/登录？注销=成功
最后，你可以在小枝模板中捕捉注销参数，如：

{%- if app.request('logout') -%}
        <div class="alert alert-success">{% trans %}Logout successful{% endtrans %}</div>
    {%- endif -%}

从5.1版开始，LogoutSuccessHandlerInterface已弃用，建议使用LogoutEvent。
Symfony\组件\安全\Http\注销\注销成功处理程序界面已弃用
但在正式文档中没有关于LogoutEvent的示例或信息

以下是LogoutEvent的文档：
https://symfony.com/blog/new-in-symfony-5-1-simpler-logout-customization
您必须创建一个事件并实现onSymfonyComponentSecurityHttpEventLogoutEvent的方法。

如果您使用的是Symfony 6及以上版本，您可以使用如下

<?php

namespace App\EventSubscriber;

use Symfony\Component\EventDispatcher\EventSubscriberInterface;
use Symfony\Component\Security\Http\Event\LogoutEvent;

class LogoutListener implements EventSubscriberInterface
{

    public function onLogout(LogoutEvent $logoutEvent): void
    {
        // Do your stuff
    }

    public static function getSubscribedEvents(): array
    {
        return [
            LogoutEvent::class => 'onLogout',
        ];
    }
}