HELP! Lets Encrypt won't install certify my public IP port forward to my Nextcloud

You cannot get certificate from Let’s Encrypt for IP. Only for domains.

That is correct, but that isn’t what @Joshua_J tried to do (even if it is, somewhat confusingly, what he suggested in the topic heading). Rather, he tried to issue a cert for 'nextcloud. That’s also invalid, of course, for two reasons:

  • The ’ character isn’t valid in a FQDN, and
  • There’s no domain name present, only (at most) a hostname.

@Joshua_J, in order to get a cert from Let’s Encrypt, you need to own or control a real internet domain–either buy one from your registrar of choice (I like lately, but there are plenty to choose from), or get a free one from and deal with their mildly-annoying renewal requirements. You’ll then need DNS records pointing that domain name to your installation.