E: The repository 'http://gb.ports.ubuntu.com/ubuntu-ports eoan-backports Release' no longer has a Release file.

[kmille36]

No description provided.

[iam-TJ]

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.

The list of architectures hosted there can be seen at https://old-releases.ubuntu.com/ubuntu/dists/eoan-backports/main/:

binary-amd64/
binary-arm64/
binary-armhf/
binary-i386/
binary-ppc64el/
binary-s390x/
cnf/
debian-installer/
dep11/
i18n/
source/