I feel that sometimes resolution of sub-domain.duckdns
and host.sub-domain.duckdns.org
fails with empty result or even timeout result. Tested resolution against Google and Cloudfare DNS servers.
Do you have a similar behaviour?
Thats how I’ve done mine.
pfSense has an updater built in so that’s handled my home.mydomain.com entry for me for a long time and has handled updating duckdns too, even though it’s basically only a backup at this point.
If you’ve got a domain, no real reason to not just handle it yourself and avoid the headaches.