Replace zero cost to “Free” for shipping method full label in WooCommerce on your child site.
Snippet Type
Execute on Child Sites
Snippet
add_filter( 'woocommerce_cart_shipping_method_full_label', 'Add_free_to_shipping_label_for_zero_cost', 10, 2 );
function Add_free_to_shipping_label_for_zero_cost( $label, $method ) {
// If shipping method cost is 0 or null, display 'Free' (except for free shipping method)
if ( ! ( $method->cost > 0 ) && $method->method_id !== 'free_shipping' ) {
$label .= ': ' . __('Free');
}
return $label;
}