We built a PKI on top of Lets Encrypt to deliver certificates to all of our users for Rainway: https://rainway.io/technology/

Similar to Plex, users run our software on their PC and then our web based client can connect to it from elsewhere.

It’s mainly used as a fallback if WebRTC fails (https://blog.rainway.io/real-time-communication-for-everyone...). If there is interest, happy to do a blog post.