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use Drupal\Core\Render\RendererInterface;
use Drupal\Component\Serialization\Json;
use Drupal\Core\Url;

    // Open link in jQuery Ajax modal window
    $renderArray['open-in-modal'] = [
      '#type' => 'link',
      '#title' => "Open in modal",
      '#url' => Url::fromRoute('entity.node.canonical', ['node' => 1], ['absolute' => TRUE]),
      '#attributes' => [
        'class' => ['use-ajax'],
        'data-dialog-type' => 'modal',
        'data-dialog-options' => Json::encode([
          'width' => 400,
        ]),
      ],
    ];
    // Turn off catching
    $renderArray['do-not-cache'] = [
      '#type' => 'markup',
      '#markup' => "Without caching",
      '#cache' => ['max-age' => 0],
    ];
    
    //disable caching:
 \!h    \Drupal::service('page_cache_kill_switch')->trigger();

    //Suffix, prefix
    $renderArray['suffix-prefix'] = [
      '#type' => 'markup',
      '#prefix' => "<div class = 'some-class'>",
      '#suffix' => "</div>",
      '#markup' => "Text with suffix, prefix",
    ];

    //Put markup inside theme wrapper container
    $renderArray['theme-wrapper-container'] = [
      '#type' => 'markup',
      [
        '#type' => 'item',
        '#markup' => "My text with theme wrapper",
      ],
      '#theme_wrappers' => [
        'container' => [
          '#attributes' => [
            'class' => ['my-style'],
          ],
        ],
      ],
    ];

    
/** @var RendererInterface $renderService */
$renderService = Drupal::service('renderer');

$body = $renderService->renderRoot($renderArray);
//or
$body = \Drupal::service('renderer')->renderRoot($renderArray);