#For Unable to 'apt update' my Ubuntu 19.04
The repositories for older releases that are not supported (like 11.04, 11.10 and 13.04) get moved to an archive server. There are repositories available at http://old-releases.ubuntu.com.
first break up this file
cp /etc/apt/sources.list /etc/apt/sources.list.bak sudo sed -i -re 's/([a-z]{2}.)?archive.ubuntu.com|security.ubuntu.com/old-releases.ubuntu.com/g' /etc/apt/sources.list
then
sudo apt-get update && sudo apt-get dist-upgrade