Install caddy. Check that it works. Get to know what a firewall is. How it works. Forward your ports from router to the machine. (I use cockpit (preinstalled on fedora) to configure my firewall)

sub.domain.com { reverse_proxy 192.168.178.192:8080 }

Replace 192.168.178.192 with the ip. And 8080 with the port and your domain obviously.

That’s it.