Get the page title from a Url in Drupal 8+

drupal_get_title_from_url_module.php

<?php

/**
 * @file
 * Contains a custom function to get the title from a Url.
 */

use Drupal\Core\Url;
use Symfony\Component\HttpFoundation\Request;

/**
 * Get the title from a Url.
 * 
 * @param \Drupal\Core\Url $url
 *   A given URL.
 *
 * @return string|null
 *   The resolved title or nothing.
 * 
 * @example Get the title for current page.
 * $current_url = Url::fromRoute('<current>');
 * $page_title = mymodule_get_title_from_url($current_url);
 *
 * @example Get the title from a given path.
 * $path = '/my-custom-page-alias';
 * $uri = 'internal:' . $path;
 * $url = Url::fromUri($uri);
 * $page_title = mymodule_get_title_from_url($url);
 * 
 * @example Get the title from an entity.
 * $url = $entity->toUrl('canonical');
 * $page_title = mymodule_get_title_from_url($url);
 * 
 * @example Get the title from a current node page.
 * $node = \Drupal::routeMatch()->getParameter('node');
 * $url = $node->toUrl('canonical');
 * $page_title = mymodule_get_title_from_url($url);
 */
function mymodule_get_title_from_url(Url $url) {
  $router = \Drupal::service('router');
  $title_resolver = \Drupal::service('title_resolver');

  $route_match = $router->match($url->toString());
  $route = $route_match['_route_object'] ?? NULL;

  if ($route) {
    try {
      $path = $url->setAbsolute(TRUE)->toString();
      $request = Request::create($path);
      $attributes = $router->matchRequest($request);
      $request->attributes->add($attributes);
      return $title_resolver->getTitle($request, $route);
    } catch (\Exception $e) {
      \Drupal::logger('mymodule')->error($e->getMessage());
    }
  }

  return NULL;
}