Hi, I cannot install a web application on ubuntu 20.04 or 18.04. It is getting an error.

Ubuntu Error:

404 Not Found [IP: 91.189.95.83 80]
Reading package lists… Done
E: The repository ’http://ppa.launchpad.net/brightbox/ruby-ng/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..

This is the application that I want to install through curl
curl https://raw.githubusercontent.com/atech/postal/master/script/install/ubuntu1604.sh | sh

Plz help me as soon as possible. I want to install it as soon as possible