Traefik can simply request certificates using the DNS verification method, as opposed to the certbot HTTP verification. (HTTP would not work with a distributed setup like this.) Alternatively, Traefik can also synchronize certificate requests using one of the many key-value stores supported (untested as of yet).

The drawback of the DNS method without synchronization between the nodes is that you run into the LetsEncrypt rate limit quite easily. My expansion to ap-southeast-1 and sa-east-1 is waiting for the LE cooldown.

Disclaimer: I'm the author of the article.