Because eoan is no longer supported it was moved out of the main archives to old-releases. Replace the entries in /etc/apt/sources.list so http://gb.ports.ubuntu.com/ubuntu-ports is replaced by https://old-releases.ubuntu.com/ubuntu and then apt update and then upgrade to a supported release with do-release-upgrade.
Because
eoan
is no longer supported it was moved out of the main archives toold-releases
. Replace the entries in/etc/apt/sources.list
sohttp://gb.ports.ubuntu.com/ubuntu-ports
is replaced byhttps://old-releases.ubuntu.com/ubuntu
and thenapt update
and then upgrade to a supported release withdo-release-upgrade
.The list of architectures hosted there can be seen at https://old-releases.ubuntu.com/ubuntu/dists/eoan-backports/main/: