function naturetour_page_attachments_alter(array &$attachments){
    $uuid = \Drupal\block\Entity\Block::load('usefull')->getPlugin()->getDerivativeId();
    $block_content = \Drupal::service('entity.repository')->loadEntityByUuid('block_content', $uuid);
    if ($block_content) {
        $field_value = $block_content->field_something_item->value;
        $attachments['#attached']['drupalSettings']['naturetour']['custom']['something_item'] = $field_value;
    }

}