I feel that sometimes resolution of sub-domain.duckdns.org and host.sub-domain.duckdns.org fails with empty result or even timeout result. Tested resolution against Google and Cloudfare DNS servers.
Question - if your domain registrar has an API to update your A/AAAA records, and your router (or other home server) lets you easily update those records via the API when your public IP changes, is there a benefit to using freedns or any other DDNS service? It seems like you don't really need them if you own a domain.