Completely stumped here. I am using SafeDNS for my DNS, which is now working fine. I'm now trying to setup a DDNS job to ping safedns every day with my IP address. This was pretty easy in Gargoyle Router (which I came from). I've downloaded luci-DDNS and installed it, I've set DDNS Service Provider to custom. I've put in the custom update URL but I have no idea what to put into the field Lookup Hostname nor Domain. SafeDNS says the customer update URL is https://[USERNAME]:[PASSWORD]@www.safedns.com/nic/update?hostname=[DOMAIN].
What this job did on Gargoyle was ping SafeDNS once a day to update my IP address.