@jsha I followed the instructions here hoping to upgrade from 0.23 to 0.28.
$ sudo apt-get update
$ sudo apt-get install software-properties-common
$ sudo add-apt-repository universe
$ sudo add-apt-repository ppa:certbot/certbot
$ sudo apt-get update
$ sudo apt-get install certbot python-certbot-apache
apt-get update didn’t work. I’m over 75% certain I tried apt-get upgrade which didn’t work either. When I ran apt upgrade, certbot --version showed 0.28. I wish I could be more precise on the method but I was trying a lot of different commands trying to find a solution.