Just a heads-up for other newbies like me; I could not find this info after searching the forum. I followed the steps to configure
ddclient on Raspbian GNU/Linux 10 (buster) with
ddclient version 3.8.3. After trying the setup the
desec.io “Check Domain Status” showed the internal LAN IP and a respective internal IPv6 address. It is because the setup process of
ddclient asks for the interface used. Un-commenting the
use=if line afterwards in the config file fixed the issue.
I also had to add the line