I was searching where you saw something about 10.8. Now I know. Thank
Maybe Hugo is waiting for ACME v2 to be launched. AFAIK, they were planning to launch it today but it is delayed :
https://community.letsencrypt.org/t/acmev2-and-wildcard-launch-delay/53654
As for testing Hiawatha 10.8, it seems possible by sending Hugo an email :
https://www.hiawatha-webserver.org/forum/topic/2694