Well, it’s 6 months later. I haven’t added a “you don’t have nc, so I can’t test your ports” message, but no one else has complained. Perhaps the language:
Google: \"open ports YOUR CLOUD SERVICE\" for information for resolving this problem.
You should probably answer \"n\" at the next prompt and disable Let's Encrypt.
This test might not work for all situations,
so if you can access Discourse at http://$HOST, you might try anyway.
is good enough. It was never a 
but really an annoyance for someone who had enough sysadmin sense to not want to use Ubuntu. It works as expected on Ubuntu (I haven’t checked other distros to see). I’m inclined to let this sleeping dog lie.