If you still have older Debian distributions, use this method to mirror releases that are no longer supported.
The old disstributions supported are: buzz, rex, bo, hamm, slink, potato, woody, sarge, etch, lenny, squeeze, wheezy, jessie, stretch, buster
{ "debian_releases": [ "buster", “stretch” ], "ubuntu_releases": ["focal"], "ubuntu_release_configs": [ { "name": "focal", "mirror": "http://old-releases.ubuntu.com/ubuntu", "is_archived": true } ]}
Fo Ubuntu, overwrite the release by using ubuntu_release_configs