For no reason other than wanting to I followed the instructions1 which were top of the search results to add an SSL certificate to my Raspberry Pi / Hugo website
sudo apt install apache2
sudo apt install python3-certbot-apache
sudo certbot --apache
I needed to provide the site address and an email address. I copied my Hugo generated static files to /var/www/html/ and then everything worked as expected but with https. One thing that later caught me out is that https by definition is on port 443 2. I have a Domoticz server and a Pi project that run on other ports but these can only be accessed from outside the house via http.