Now this is not a big deal as you can do wildcard with Cloudflare as it is so you would need to use our DNS anyhow if you wanted to use wildcards, but yes as we use DNS-01 challenge you will be unable to use a external DNS host.
DNS-01 means that our scripts gets a key from LE while creating the record and we then must make a DNS record in BIND for _acme-challenge so that the checks will pass. This means external DNS is out of the question as there is no standard for external DNS updating with other providers.
This also means that when getting a wildcard certificate it takes a LOT longer to finish. But good news if you don't use a wildcard * domain entry, we still use HTTP-01 for validation so it will still work with external DNS.
