With these settings I can plug my RPi into a router and it will configure a web URL to it’s routers IP address (although I haven’t set and UPNP stuff).
I tested with
sudo ddclient -daemon=0 -debug -verbose -noquiet
Returns this at the bottom
SUCCESS: rpi: skipped: IP address was already set to 'My WAN IP'.
Also I edited my SSH config since apparently my home NAT router didn’t like keeping the connections alive. These settings went at the bottom of sshd_config – initially I used ServerAlive, which stopped SSH from working :/
ClientAliveInterval 300 ClientAliveCountMax 24