gistfile1.txt

  $parameters = new MenuTreeParameters();
  $parameters->setMaxDepth(2)->onlyEnabledLinks();

  $menuTreeService = Drupal::menuTree();

  $tree = $menuTreeService->load('main', $parameters);

  if ($tree) {
    $build = $menuTreeService->build($tree);

    // Switch the theme back from menu--main. While this *is* the main menu, we don't want it to pick up that styling.
    $build['#theme'] = 'menu__footer';
  }