How to keep Drupal paragraphs from "bleeding through" into languages where no translation exists - see https://www.mediacurrent.com/blog/deep-dive-translating-paragraphs

mysite.module

<?php

/**
 * Implements hook_ENTITY_TYPE_access() for paragraph entities.
 */
function mysite_paragraph_access(\Drupal\paragraphs\Entity\Paragraph $entity, $operation, $account) {
  // Show paragraphs only if they exist in the current language; don't fall
  // back to the default language.
  if ($operation == 'view') {
    $current_language = \Drupal::languageManager()->getCurrentLanguage()->getId();
    $available = $entity->getTranslationLanguages();
    if (!isset($available[$current_language])) {
      return \Drupal\Core\Access\AccessResult::forbidden();
    }
  }
  return \Drupal\Core\Access\AccessResult::neutral();
}