It’s not quite the same problem – a “Timeout after connect” means that it was able to connect. It just stopped working after that.
It probably means that there isn’t a firewall blocking all port 80 traffic, but there is some other configuration issue.
Even if you have port 80 forwarded to a different server, you could have that server reverse proxy the ACME validation requests to your Nextcloud server. HTTP validation is still an option.
I redirected external port 80 to the nextcloud server on port 443, but for some reason the url fails to load http://blucap.no-ip.org, but https://blucap.no-ip.org does load.
Interesting. I just tried curl http://blucap.no-ip.org and got a timeout. Maybe your ISP is blocking port 80? Maybe your router or Nextcloud is firewalling it off?
What did you have on port 80 previously, and were you able to access it from outside your network?
Ah, I recall hearing about another person with an ASUS router who had trouble like this. I think it turned out to be DDoS protection activating due to more than 32 simultaneous inbound connections from Let’s Encrypt staging (which sends more queries than prod). Is this against staging or production?