How to install software or upgrade from an old unsupported release? https://askubuntu.com/questions/91815/how-to-install-software-or-upgrade-from-an-old-unsupported-release
apt-get update returns 404 errors for Debian repository on Ubuntu 14.04 https://askubuntu.com/questions/1116509/apt-get-update-returns-404-errors-for-debian-repository-on-ubuntu-14-04
https://www.geekersdigest.com/apt-etc-apt-sources-list-for-every-debian-release/#debian-8-jessie
deb http://archive.debian.org/debian/ jessie main contrib non-free
deb http://archive.debian.org/debian-security jessie/updates main contrib non-free