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

Solution 1:

I got rid of the error message on Ubuntu 20.04 by removing the ppa repository. It took me a long time to find out the exact command argument, so this might help others :-). I used the command:

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

After that, the following commands do not generate any errors:

sudo apt update
sudo apt-get update

Solution 2:

I stumbled into these messages

~$ sudo add-apt-repository ppa:certbot/certbot
 This is the PPA for packages prepared by Debian Let's Encrypt Team and backported for Ubuntu.

Note: Packages are only provided for currently supported Ubuntu releases.
 More info: https://launchpad.net/~certbot/+archive/ubuntu/certbot
Press [ENTER] to continue or Ctrl-c to cancel adding it.

Hit:1 http://ca-central-1.ec2.archive.ubuntu.com/ubuntu focal InRelease
Get:2 http://ca-central-1.ec2.archive.ubuntu.com/ubuntu focal-updates InRelease [111 kB]              
Get:3 http://ca-central-1.ec2.archive.ubuntu.com/ubuntu focal-backports InRelease [98.3 kB]           
Get:4 http://security.ubuntu.com/ubuntu focal-security InRelease [107 kB]                             
Ign:5 http://ppa.launchpad.net/certbot/certbot/ubuntu focal InRelease                                 
Get:6 http://ca-central-1.ec2.archive.ubuntu.com/ubuntu focal-updates/main amd64 Packages [588 kB]
Get:7 http://ca-central-1.ec2.archive.ubuntu.com/ubuntu focal-updates/universe amd64 Packages [666 kB]
Err:8 http://ppa.launchpad.net/certbot/certbot/ubuntu focal Release                                      
  404  Not Found [IP: 91.189.95.83 80]
Reading package lists... Done                  
E: The repository 'http://ppa.launchpad.net/certbot/certbot/ubuntu focal Release' does not have a Release file.
N: Updating from such a repository can't be done securely, and is therefore disabled by default.
N: See apt-secure(8) manpage for repository creation and user configuration details.

by following Ubuntu 18.04 certbot installation instructions on Ubuntu 20.04.

I should've followed the Ubuntu 20.04 certbot installation instructions, which avoid the command sequence sudo add-apt-repository ppa:certbot/certbot followed by sudo apt install python-certbot-nginx and simply execute

sudo apt install certbot python3-certbot-nginx

Note that the 20.04-friendly command uses python3 in the command, and not just python.

To be fair, I wasn't the only one dealing with this issue. This other post about solutions that offer the -r option to remove repositories helped me figure out in which direction a solution to my issue could be.

See @vinyll's answer for "A one-liner Certbot install is available with the uninstaller included. Works also on Ubuntu 20.04." I did not follow that route because I'm not to keen to uninstall packages without being absolutely certain what they're dependencies for. Since I wasn't 100% certain at the time, it was easier to just follow the installation instructions for the proper OS than uninstall it risking eliminating needed dependencies without being aware.