function my_landing_page_preprocess(&$variables) {
  if (isset($variables['entity'])) {
    $node = $variables['entity'];

      my_analytics_get_landing_page_analytics($node);
  }
}

function my_analytics_get_landing_page_analytics($node) {
  if ($node instanceof Node && $node->getEntityTypeId() == 'node' && $node->getType() == 'landing_page') {

    if ($node->hasField('field_page_type') && count($node->get('field_page_type')->getValue()) > 0) {
      my_analytics_add_tags_global([
        'TagID_channel' => $node->get('field_page_type')->getValue()[0]['value'],
      ]);
    }

  }
}

function my_analytics_add_tags_global(array $tags) {
  if (isset($GLOBALS['my_dtm_global_tags']) && is_array($GLOBALS['my_dtm_global_tags'])) {
    $GLOBALS['my_dtm_global_tags'] = array_merge($GLOBALS['my_dtm_global_tags'], $tags);
  }
  else {
    $GLOBALS['my_dtm_global_tags'] = $tags;
  }
}

function my_analytics_add_set_tags(array &$build, array $tags) {
  if (!empty($build['#attached']['drupalSettings']['my_analytics']['setTags'])) {
    $build['#attached']['drupalSettings']['my_analytics'['setTags'] = [];
  }

  // Search for global tags added from other modules.
  if (isset($GLOBALS['my_dtm_global_tags']) && is_array($GLOBALS['my_dtm_global_tags'])) {
    $tags = array_merge($tags, $GLOBALS['my_dtm_global_tags']);
  }

  foreach ($tags as $tag_id => $tag_value) {
    $build['#attached']['drupalSettings']['my_analytics']['setTags'][] = [
      'id' => $tag_id,
      'value' => $tag_value,
    ];
  }
}