Hi There,
Thanks for writing in! Could you please try adding the following code into your child theme's functions.php file. If you don't have a child theme yet, please follow this guide first (https://theme.co/apex/forum/t/setup-how-to-setup-child-themes/57).
//add hatom data
function add_suf_hatom_data($content) {
$t = get_the_modified_time('F jS, Y');
$author = get_the_author();
$title = get_the_title();
if (( is_front_page() && is_home() ) || is_front_page() || is_home() || is_singular() || is_archive() ) {
$content .= '<div class="hatom-extra" style="display:none;visibility:hidden;"><span class="entry-title">'.$title.'</span> was last modified: <span class="updated"> '.$t.'</span> by <span class="author vcard"><span class="fn">'.$author.'</span></span></div>';
}
return $content;
}
add_filter('the_content', 'add_suf_hatom_data');
add_filter('the_excerpt', 'add_suf_hatom_data');
Hope that helps.