Install and configure Nginx:

$ sudo apt update
$ sudo apt install nginx
$ sudo rm /etc/nginx/sites-enabled/default
$ sudo vi /etc/nginx/sites-available/MYSITE  # See below
$ sudo ln -s /etc/nginx/sites-available/MYSITE /etc/nginx/sites-enabled
$ sudo systemctl restart nginx

The /etc/nginx/sites-available/MYSITE config file should look like so:

server {
  listen 80;
  server_name MYSITE.COM WWW.MYSITE.COM;
}

server {
  listen 443 ssl;
  server_name MYSITE.COM WWW.MYSITE.COM;
  server_tokens off;

  # If you use nginx as reverse-proxy
  location / {
    proxy_pass http://localhost:8080;
    proxy_set_header Host $host;
  }
}

Install certbot:

$ sudo apt update
$ sudo apt install software-properties-common
$ sudo add-apt-repository ppa:certbot/certbot
$ sudo apt update
$ sudo apt install certbot python-certbot-nginx

Create the certificate:

$ sudo certbot --nginx --agree-tos --redirect --uir --hsts --staple-ocsp --email ME@MYSITE.COM -d MYSITE.COM -d WWW.MYSITE.COM

You could potentially use the --must-staple option to enable the OCSP “must staple” extension, but it doesn’t work well with Firefox (to fix in your Firefox browser: go to about:config, and set security.ssl.enable_ocsp_must_staple to false).

The arguments are:

• --nginx: Use Nginx for authentication and install certificate for Nginx
• --agree-tos: Agree with Let’s Encrypt terms of service
• --redirect: Add Nginx config to redirect HTTP to HTTPS
• --uir: Add Content-Security-Policy: upgrade-insecure-requests to HTTP responses
• --hsts: Add Strict-Transport-Security header to HTTP responses
• --staple-ocsp: Enable OSCP stapling (allow browser to skip verification of whether the SSL certificate has been revoked or not)
• --email: Email address to use to register with Let’s Encrypt, and potentially for recovery