Hello,
Navigate to Appearance > Customize > WooCommerce > Default product sorting.
To show an out of stock product at the end of the archive pages, Try to add the following code in the function.php of the child theme.
add_filter('posts_clauses', 'order_by_stock_status');
function order_by_stock_status($posts_clauses) {
global $wpdb;
// only change query on WooCommerce loops
if (is_woocommerce() && (is_shop() || is_product_category() || is_product_tag() || is_product_taxonomy())) {
$posts_clauses['join'] .= " INNER JOIN $wpdb->postmeta istockstatus ON ($wpdb->posts.ID = istockstatus.post_id) ";
$posts_clauses['orderby'] = " istockstatus.meta_value ASC, " . $posts_clauses['orderby'];
$posts_clauses['where'] = " AND istockstatus.meta_key = '_stock_status' AND istockstatus.meta_value <> '' " . $posts_clauses['where'];
}
return $posts_clauses;
}
Best Regards.