The Certbot documentation makes it look like you can only install Certbot using snapd. That doesn’t appear to be true, at least for initial install. This works fine:
sudo apt install certbot
sudo apt install python3-certbot-apache
And then the usual steps after that:
sudo certbot --apache -d example.com
I haven’t been through the cert renewal process yet on Ubuntu 20.04, but I don’t see why it wouldn’t work, since it essentially follows the same steps.