Install latest version of certbot.
This makes Certbot work on Ubuntu 20.04 Focal. Probably for latest Debian as well.
Run the following command with a sudoer:
curl -o- https://raw.githubusercontent.com/vinyll/certbot-install/master/install.sh | bash
curl -o- https://raw.githubusercontent.com/vinyll/certbot-install/master/uninstall.sh | bash
You may prefer the regular installation of certbot from official PPA.
However, if you experiment the following error with Ubuntu Focal 20.04, this install should solve.
AttributeError: module 'acme.challenges' has no attribute 'TLSSNI01'
This is also interesting if you need to work with the latest release of certbot.