Here’s an overview of the Let’s Encrypt DNS challenge type in case you haven’t seen it: letsencrypt.org/docs/challenge-types/#dns-01-chal…
Basically, when Traefik goes to request or renew a certificate, Let’s Encrypt tries to look up a special DNS record on your domain so you can prove that the request for the certificate is legit. To make that work, Traefik first hits your DNS provider via API and temporarily inserts that special record so it’s there when Let’s Encrypt performs the lookup for it. In my particular case, I’m using self-hosted PowerDNS and it’s built-in API (configured to only respond via a Wireguard tunnel). But you don’t have to self-host DNS for this to work… Traefik has a long list of supported providers: doc.traefik.io/traefik/https/acme/#dnschallenge