Symfony attributes routes not taken into account

I have an existing Symfony 5.2 application running on PHP 8 that uses YAML config for routes.

I'd like to convert it to use attributes instead. I added a config/routes/annotations.yaml file:

  resource: ../../src/UserInterface/Web/
  type: annotation

  resource: ../../src/Kernel.php
  type: annotation

(yes, my controllers are under src/UserInterface/Web!)

I removed my routes from my .yaml config files, and added attributes to controllers:

use Symfony\Component\Routing\Annotation\Route;

class HomeController
    #[Route('/', name: 'homepage')]
    public function index(Request $request): Response { ... }

But my home page now displays the "Welcome to Symfony" page. I tried:

bin/console debug:router

but it does not display the homepage route. I tried using Doctrine annotations instead:

 * @Route("/", name="homepage")
public function index(Request $request): Response { ... }

with no luck either. I tried clearing the cache:

bin/console cache:clear

But the issue persists. What did I miss?