The repository ‘http://ppa.launchpad.net/certbot/certbot/ubuntu focal Release’ does not have a Release file

When updating the package information index on Ubuntu 20.04, you may encounter the error below:

The repository ‘http://ppa.launchpad.net/certbot/certbot/ubuntu focal Release’ does not have a Release file.

To fix the error, run the commands below one by one:

$ sudo apt-add-repository -r ppa:certbot/certbot
$ sudo apt update