WordPress with static posts page and custom permalink structure doesn’t find posts with numeric permalinks

With some help I was able to get it working with this:

add_action('init', 'journal_urls');
  function journal_urls() {
      add_rewrite_rule(
          '^journal/([^/]*)$',
          'index.php?name=$matches[1]',
          'top'
      );
  }

Maybe someone can benefit from this in the future.