Google maintains mirrors of the Debian apt repos at:
https://packages.cloud.google.com/mirror/cloud-apt
I have these entries in my sources:
deb https://packages.cloud.google.com/mirror/cloud-apt/buster buster main
deb https://packages.cloud.google.com/mirror/cloud-apt/buster-security buster-security main
deb https://packages.cloud.google.com/mirror/cloud-apt/buster-updates buster-updates main
deb https://packages.cloud.google.com/mirror/cloud-apt/buster-backports buster-backports main
The first one "buster" works fine.
The other three "buster-security", "buster-updates" and "buster-backports" all return 404 not found.
The instance in question does not have http/https egress to the rest of the internet so I can't use the Debian repos.
Can anyone explain where the other repos have gone, or have some better advice as to the correct entries for sources.list?