There may be other problems, but this will be a definite blocker.
…which is your problem. Let’s Encrypt will only issue five certs for a given set of FQDNs within a week. You exhausted that limit within 45 minutes. Once you did that, any further attempt at installation was guaranteed to fail.
I did the normal installation the first time, an error occurred.
I did the second installation on digitalocean with one click, the same error happened.
It hasn’t worked since the first try.
I have been running discourse with cloudflare (hosted on vultr) for almost an year now. If You have a budget, maybe consider hiring someone to do it for you if you can’t figure out the exact problem. Feel free to post in marketplace
That means there’s something funky with your Cloudflare setup. If Cloudflare is running in DNS-only mode, it should function identically to any other DNS provider, Google included. If it doesn’t, that’s a Cloudflare bug, and you’ll need to reach out to their support team.
…and if it’s a Cloudflare bug, it isn’t a universal one–I personally manage two Discourse sites that are using Cloudflare DNS, and I’m pretty sure I’m not the only one.