apt update: The repository no longer has a Release file

I have some Ubuntu Server 20.04 installations, but just for one of them happens the following:

sudo apt update
... password
Hit:1 groovy InRelease
Ign:2 groovy InRelease
Ign:3 groovy-updates InRelease
Hit:4 groovy-pgdg InRelease
Ign:5 groovy-backports InRelease
Ign:6 groovy-security InRelease
Err:7 groovy Release 404 Not Found [IP: 200.236.31.4 80]
Err:8 groovy-updates Release 404 Not Found [IP: 200.236.31.4 80]
Err:9 groovy-backports Release 404 Not Found [IP: 200.236.31.4 80]
Err:10 groovy-security Release 404 Not Found [IP: 200.236.31.4 80]
Reading package lists... Done
E: The repository ' groovy Release' no longer has 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.
E: The repository ' groovy-updates Release' no longer has 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.
E: The repository ' groovy-backports Release' no longer has 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.
E: The repository ' groovy-security Release' no longer has 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.

What happened this? and how to solve?

1 Answer

In my case, I had several Ubuntu 20.10 Docker images running on my server. Due to the deprecation of Ubuntu 20.10, all of the PPA releases are gone.
I solved it by deploying Ubuntu 20.04 images instead and updating the packages for that version. I plan on deploying new images at 22.04, once that's been out for a while.

From experience, even though it's possible, it's not recommended to try downgrading the packages and PPA on your machine.

While this is generally a duplicate of What can I do if a repository/PPA does not have a Release file?, this is specific to Ubuntu deprecating versions in a generally unexpected manner.