Let's Encrypt does not support dns-persist-01 yet according to Dns-persist-01 deployment status and timeline - #17 by aarongable anyway. And the Certbot dev team is quite small, so implementation of new features can take a while.
Edit: looks like there already is a PR for it on the Certbot GH repo though: Add dns-persist-01 challenge type to the manual plugin by wgreenberg · Pull Request #10633 · certbot/certbot · GitHub. You can follow that.