The Caddy[1] webserver also has built-in ACME. It has all the problems Rachel mentioned, of course, because now it's an ACME client embedded in an even bigger piece of software, but it's handy for sure!

I don't know much about Caddy scalability but it's worked great for my personal sites.

[1] https://caddyserver.com/

It scales to hundreds of thousands of sites.