The problem is almost certainly that debatehosting.co doesn’t (or perhaps didn’t) resolve to your virtual machine and/or ports 80/443 are blocked by something on the server or upstream. If you’ve done this a bunch of times then it’s the case that you’ve hit let’s encrypt rate limiting and you’ll need to try again. But you should use www rather than the apex domain, and if you do that, it’ll be a new request and you won’t be rate limited since you haven’t requested any certs for that hostname yet.
Did discourse-setup say something like “I can’t access your server via the domain name” did you do something to get it to continue anyway?
Did you use discourse-setup or did you do this all by hand, old school, so no check was done.?
They don’t matter. Let’s Encrypt doesn’t use those anymore and I don’t think Discourse does anything with them any more either.
If you do use cloudflare, don’t use orange cloud. When I checked a minute ago, it resolves to a single IP address. Nothing is answering on that address on port 80 or 443, but I think that’s because NGINX refuses to crank up.