This is a clean stable 20.04 install of the Raspberry PI image.
$ sudo apt update
[sudo] password for admn:
Ign:1 http://ppa.launchpad.net/certbot/certbot/ubuntu focal InRelease
Hit:2 http://ports.ubuntu.com/ubuntu-ports focal InRelease
Get:3 http://ports.ubuntu.com/ubuntu-ports focal-updates InRelease [106 kB]
Err:4 http://ppa.launchpad.net/certbot/certbot/ubuntu focal Release
404 Not Found [IP: 2001:67c:1560:8008::15 80]
Hit:5 http://ports.ubuntu.com/ubuntu-ports focal-backports InRelease
Get:6 http://ports.ubuntu.com/ubuntu-ports focal-security InRelease [107 kB]
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.
I would expect that this PPA should either not be included in the default image, or that the Release file should be there. I suspect that this is a stripped-down Ubuntu server image, and that the PPA should not be included in the image.
But which, or another option?