your_extension.module

<?php

/**
 * @file
 * Code for your_extension module.
 *
 * Adds a <noscript> tag holding the text set in the configuration form,
 * shown only when JavaScript is disabled, plus a
 * div[data-your-extension-time] element that js/your_extension.js fills
 * with the page load time. Attaches the your_extension/global library to
 * every page.
 */

declare(strict_types=1);

/**
 * Implements hook_page_attachments().
 */
function your_extension_page_attachments(array &$attachments): void {
  $attachments['#attached']['library'][] = 'your_extension/global';
}

/**
 * Implements hook_page_bottom().
 */
function your_extension_page_bottom(array &$page_bottom): void {
  /** @var \Drupal\your_extension\YourExtensionService $your_extension_service */
  $your_extension_service = \Drupal::service('your_extension.service');

  $text = $your_extension_service->getText();

  if (!empty($text)) {
    $page_bottom['your_extension'] = [
      '#type' => 'html_tag',
      '#tag' => 'noscript',
      '#value' => $text,
    ];
  }

  $page_bottom['your_extension_time'] = [
    '#type' => 'html_tag',
    '#tag' => 'div',
    '#attributes' => [
      'data-your-extension-time' => TRUE,
    ],
  ];
}