When configuring the DDNS scripts, the "Public" URL used to find the external IP is not accepted on RUTX GUI 7.02.7, which is totally wrong.
I use an external script on my own server to obtain the public IP the router has, and then update consequently my dynamic DNS domain hosted at changeip.com. The script is not accepted because as "URL to detect" it is expecting ONLY A DOMAIN, and not a correctly formatted URL. So I cannot configure DDNS from GUI and have to reconfigure it by manually editing the file via SSH in /etc/config/ddns and adding the correct URL to "option ip_url 'http://<mydomain.is>/<my_path_to_ip_script.php>' "
This is a bug in GUI. Please fix.