If you find yourself updating an old Debian/need to upgrade and get this error, generally you just have to update sources.list by setting all hostname references to archive.debian.org
Backup your sources.list
cp /etc/apt/sources.list /etc/apt/sources.list-bk
Change deb.debian and snapshot.debian
sed -i s/"deb.debian"/"archive.debian"/g /etc/apt/sources.list
sed -i s/"snapshot.debian"/"archive.debian"/g /etc/apt/sources.list
root@206f261b684c:/# apt update
Ign:1 http://deb.debian.org/debian buster InRelease
Ign:2 http://deb.debian.org/debian-security buster/updates InRelease
Ign:3 http://deb.debian.org/debian buster-updates InRelease
Err:4 http://deb.debian.org/debian buster Release
404 Not Found [IP: 151.101.214.132 80]
Err:5 http://deb.debian.org/debian-security buster/updates Release
404 Not Found [IP: 151.101.214.132 80]
Err:6 http://deb.debian.org/debian buster-updates Release
404 Not Found [IP: 151.101.214.132 80]
Reading package lists... Done
E: The repository 'http://deb.debian.org/debian buster Release' does not have a Release file.
N: Updating from such a repository can't be done securely, and is therefore disabled by default.
N: See apt-secure(8) manpage for repository creation and user configuration details.
E: The repository 'http://deb.debian.org/debian-security buster/updates Release' does not have a Release file.
N: Updating from such a repository can't be done securely, and is therefore disabled by default.
N: See apt-secure(8) manpage for repository creation and user configuration details.
E: The repository 'http://deb.debian.org/debian buster-updates Release' does not have a Release file.
N: Updating from such a repository can't be done securely, and is therefore disabled by default.
N: See apt-secure(8) manpage for repository creation and user configuration details.
root@206f261b684c:/# cat /etc/apt/sources.list
# deb http://snapshot.debian.org/archive/debian/20240612T000000Z buster main
deb http://deb.debian.org/debian buster main
# deb http://snapshot.debian.org/archive/debian-security/20240612T000000Z buster/updates main
deb http://deb.debian.org/debian-security buster/updates main
# deb http://snapshot.debian.org/archive/debian/20240612T000000Z buster-updates main
deb http://deb.debian.org/debian buster-updates main
root@206f261b684c:/# sed s/"deb.debian"/"archive.debian"/g /etc/apt/sources.list
# deb http://snapshot.debian.org/archive/debian/20240612T000000Z buster main
deb http://archive.debian.org/debian buster main
# deb http://snapshot.debian.org/archive/debian-security/20240612T000000Z buster/updates main
deb http://archive.debian.org/debian-security buster/updates main
# deb http://snapshot.debian.org/archive/debian/20240612T000000Z buster-updates main
deb http://archive.debian.org/debian buster-updates main
root@206f261b684c:/# sed -i s/"deb.debian"/"archive.debian"/g /etc/apt/sources.list
root@206f261b684c:/# sed -i s/"snapshot.debian"/"archive.debian"/g /etc/apt/sources.list
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