Edit Order Received title on thank you page

Try this in functions.php:

add_filter( 'the_title', 'title_order_received', 10, 2 );
function title_order_received( $title, $id ) {
  if ( is_order_received_page() && get_the_ID() === $id ) {
    $title = "Registration received";
  }
  return $title;
}

Credit:
https://www.barrykooij.com/change-woocommerce-thank-page-title/

If it works for you it should go in functions.php for your child theme to avoid being overwritten by updates.

Thanks again, Lorro for your answer. This helped me today.