I think that cPanel only works for PHP-based stuff. If it had a reverse proxy, you might be able to make it work, but it would be hard. If it did have a reverse proxy and you knew a lot about how it worked, you could install Discourse on its own server, see how that worked, then change the ports in the app.yml file to whatever the reverse proxy would point to and then you could conceivably copy that app.yml to the cPanel server and then it might work.
But if all of that doesn’t make complete sense, you’ll be better of just sticking with installing Discourse on its own server with a standard install.