Валидная разметка для Yoast SEO

wpseo-breadcrumbs-tags.php

<?php
if ( function_exists( 'wpseo_custom_breadcrumb' ) ) {

  function wpseo_custom_breadcrumb_output_wrapper( $wrapper ) {
    $wrapper = 'ol';
    return $wrapper;
  }
  add_filter( 'wpseo_breadcrumb_output_wrapper', 'wpseo_custom_breadcrumb_output_wrapper' );

  function wpseo_custom_breadcrumb_single_link_wrapper( $wrapper ) {
    $wrapper = 'li';
    return $wrapper;
  }
  add_filter( 'wpseo_breadcrumb_single_link_wrapper', 'wpseo_custom_breadcrumb_single_link_wrapper' );

}