Following: http://symfony.com/doc/4.0/setup.html

• composer create-project symfony/skeleton my-project
• cd my-project
• composer require server
• php bin/console server:run

Quote:

Open your browser and navigate to http://localhost:8000/. If everything is working, you'll see a welcome page.

Instead get:

Sorry, the page you are looking for could not be found.

(2/2) NotFoundHttpException
No route found for "GET /"

In 3.3 there used to be a welcome. The 4.0 skeleton doesn't create any kind of controller or template at all, so you have to do that yourself.