Symfony4 - How to connect several options for the design / design of the site, and organize switching between them?

Question

symfony

For example, there are two options for website design - standard and for mobile applications. And accordingly, it is necessary to switch between these design options depending on the device from which the user entered.

Answer 1

how the switching effect is not clear
1) either make an adaptive layout and then everything happens by itself
2) either sculpt a subdomain for mobile devices,
and then either use multi-routes

/**
    *  @Route("/", name="mobile_homepage", host="m.example.com")
     * @Route("/", name="homepage")
     */
     public function homepage(Request $request)
    {
        $currentHost = $request->getHttpHost();
         var_dump($currentHost);die;
    }

or duplicate actions

/**
     * @Route("/", name="mobile_homepage", host="m.example.com")
     */
    public function mobileHomepage()
    {
        // ...
    }

    /**
     * @Route("/", name="homepage")
     */
    public function homepage()
    {
        // ...
    }

Answer 2

Thanks to everyone who replied and for the Kernel idea. Once again, I "climbed" to the docks, and found another solution.
It turns out that Symfony4 compiles the configuration, controllers, extensions, templates, etc., and puts it all in the /var/cache folder, where the path to the templates is already hardcoded. And changing it after that in the application most likely will not work.
So we initially need to create 2 configurations, and in our case, depending on $_SERVER['SERVER_NAME'] choose one of them.
To do this, we make changes to config/packages/twig.php

<?php		
    if (isset($_SERVER['SERVER_NAME']) && preg_match("/m.example.com/i", $_SERVER['SERVER_NAME'])) {
  
      $container->loadFromExtension('twig', [
          'paths' => [
                  '%kernel.project_dir%/templates_mobile' => null
                  ],
                  
          // ... другие опции конфига
      ]);
    } else {
      $container->loadFromExtension('twig', [
          'paths' => [
                  '%kernel.project_dir%/templates' => null
                  ],
                  
          // ... другие опции конфига
      ]);
    }

If you have configuration in twig.yaml file, rewrite it in twig.php format and then delete twig.yaml file.
And we make changes to src/Kernel.php

<?php
   // ...
   
   public function getCacheDir(): string
   {
    if (isset($_SERVER['SERVER_NAME']) && preg_match("/m.example.com/i", $_SERVER['SERVER_NAME'])) {	
      return $this->getProjectDir()."/var/cache_mobile/".$this->environment;
    } else {
      return $this->getProjectDir()."/var/cache/".$this->environment;
    }
   }
   
   // ...