I have just done a fresh install of ISPConfig on Ubuntu 18.04. When I create new websites through the control panel Let's Encrypt seems to work fine, I can access the new websites through https without any errors or problems. Which makes me think apache is configured correctly. But for the Control Panel itself it doesn't work. I cannot access it through http and through https I get the not secure icon and if I click that, it says the certificate is invalid. I did create the certificate when I installed following the "Perfect Server" guide on here. I have tried reconfiguring and create a new certificate but that didn't help.
The certificate you created is a so-called 'self-signed SSL certificate', such a certificate must show a warning in the browser. So what you see is absolutely ok, just click on accept in the warning to access ISPConfig. If you want to replace your self-signed SSL certificate with one from Let's encrypt, then follow this guide: https://www.howtoforge.com/tutorial/securing-ispconfig-3-with-a-free-lets-encrypt-ssl-certificate/
Ah - yes, of course. That makes sense. One more question - after installing ISPConfig I can no longer access files in the web root - var/www/html/ through a browser. Is that also because I need to create an ISPConfig site for the server FQDN?
