It’s wild when you accidentally step upon something intended, yet benign? Something like that happened a few months back when I was volunteering at DEF CON Delhi Group 9111, managing the CTF infrastructure.
The story As any sane & quick CTF organizer, the approach was simple. Registrations and challenge descriptions hosted on CTFd. Challenges themselves were dockerized and deployed as their own containers inside a Ubuntu Server VM. A nginx reverse-proxy to handle traffic on the basis of FQDN (VHOST).