RenderArrayNonHtmlSubscriberTestController.php

<?php

namespace Drupal\render_array_non_html_subscriber_test;

use Drupal\Core\Controller\ControllerBase;
use Symfony\Component\HttpFoundation\Response;
class RenderArrayNonHtmlSubscriberTestController extends ControllerBase {
    
    /**
     * @return string
     */
    public function rawString() {
        return new Response($this->t('Raw controller response.'));
    }
    
    /**
     * @return array
     */
    public function renderArray() {
        return [
            '#type' => 'html_tag',
            '#tag' => 'p',
            '#value' => $this->t('Controller response successfully rendered.'),
        ];
    }

}