You will find many issues on here pointing out documentation that has not been properly updated to remove ratel (the port 8000 website). In v21.03+ the recommended use of ratel is by using play.dgraph.io and connecting to the http port on your alpha from there (often http://127.0.0.1:8080 for those running this with port-forward or locally).
When ratel was included it just produced the same html,css,js that play.dgraph.io gives you anyway so it is exactly the same as running locally - unless you are running in some sort of walled garden without access to the internet, which is very uncommon. In that case you can run your own ratel using the ratel container.