Well, every timer needs a service to activate. And at a cursory glance, this project has oneshot services, which is what I would expect for something like this. So your units (e.g. a webserver) would take After= and Wants=/Requires= on the given oneshot services.

This project looks neat! I might give it a try. I had never heard of dehydrated, but I don't particularly love certbot, and would certainly be willing to try.