Here is what it looks like:
sudo apt update
Err:15 http://security.ubuntu.com/ubuntu impish-security Release
404 Not Found [IP: 2620:2d:4000:1::19 80]
Reading package lists... Done
E: The repository 'http://security.ubuntu.com/ubuntu impish-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.
