How to install Let's Encrypt SSL certificate
Make sure your site is available in all its aliases, e.g: www.yourdomain.tld
All DNS A / AAAA records of the site and aliases must point to the server.
Then inside ISPConfig web hosting control panel perform these tasks:
- Go to Sites module
- Click on the site you want the certificate
- Check the Let's Encrypt SSL field
- Click on Save button