Internally, WooCommerce uses WordPress’ wp_safe_redirect() which does not allow redirects to external hosts. In order to get around this, we must add our desired host to the whitelist. The whitelist can be modified using the allowed_redirect_hosts which has been demonstrated below:
/**
* Adds example.com to the list of allowed hosts when redirecting using wp_safe_redirect()
*
* @param array $hosts An array of allowed hosts.
* @param bool|string $host The parsed host; empty if not isset.
*/
add_filter( 'allowed_redirect_hosts', 'wpse_allowed_redirect_hosts', 10, 2 );
function wpse_allowed_redirect_hosts( $hosts, $host ) {
$hosts[] = 'example.com';
return $hosts;
}
Use the code above along with your original code (customizing the host as needed) to allow WooCommerce users to be redirected to an external domain after completing the registration process.