By the way, check out this thread: Using Let's Encrypt for a local web server
I’ve started strongly recommending that any IoT deployment of ACME send traffic through a proxy controlled by the developer. We’ve seen a lot of problems where IoT ACME clients have bugs that result in excessive traffic in aggregate, but that are hard for the developer to debug because they can’t see what the deployed clients are doing. Pushing traffic through the proxy means that you can see when your clients start sending too much traffic, can shut it off if necessary, and can debug and redeploy.