Order posts in archive page based on child terms

order.archive.php

add_filter( 'posts_clauses', function( $pieces, $obj ) {
    global $wpdb;

    $pieces['join'] .= " LEFT JOIN `$wpdb->term_relationships` AS trs ON ($wpdb->posts.ID = trs.object_id)";
    $pieces['join'] .= " LEFT JOIN `$wpdb->term_taxonomy` AS tt ON (trs.term_taxonomy_id = tt.term_taxonomy_id)";
    $pieces['join'] .= " LEFT JOIN `$wpdb->terms` AS t ON (tt.term_id = t.term_id)";
    $pieces['join'] .= " LEFT JOIN `$wpdb->term_taxonomy` AS parent ON (parent.parent = trs.term_taxonomy_id)";
    $pieces['join'] .= " LEFT JOIN `$wpdb->terms` AS parent_terms ON (parent.term_id = parent_terms.term_id)";

    $pieces['where'] .= " AND (tt.taxonomy = '*YOUR_TAXONOMY*')";

    $pieces['orderby'] = "IFNULL(parent_terms.slug, t.slug) ASC";

    $pieces['limits'] = "LIMIT 0, 999";
  return $pieces;
}, 10, 2 );