How did I fix «Repository 'http://ftp.debian.org/debian stable InRelease' changed its 'Codename' value from 'buster' to 'bookworm'» in Debian 10 (Buster)?

E: Repository 'Index of /debian stable InRelease' changed its 'Codename' value from 'buster' to 'bookworm'
E: Repository 'http://security.debian.org buster/updates InRelease' changed its 'Suite' value from 'stable' to 'oldoldstable'
E: Repository 'Index of /debian buster-updates InRelease' changed its 'Suite' value from 'stable-updates' to 'oldoldstable-updates'
E: Repository 'Index of /php/ buster InRelease' changed its 'Suite' value from '' to 'buster'
E: Repository 'http://ftp.us.debian.org/debian buster-proposed-updates InRelease' changed its 'Suite' value from 'proposed-updates' to 'oldoldstable-proposed-updates'
E: Failed to download some files
W: Failed to fetch http://ftp.debian.org/debian/dists/stable/InRelease:
W: Failed to fetch http://ftp.debian.org/debian/dists/buster-updates/InRelease:
W: Failed to fetch http://security.debian.org/dists/buster/updates/InRelease:
W: Failed to fetch http://ftp.us.debian.org/debian/dists/buster-proposed-updates/InRelease:
W: Failed to fetch https://packages.sury.org/php/dists/buster/InRelease:
E: Some index files failed to download. They have been ignored, or old ones used instead.

Solved by:

apt-get update --allow-releaseinfo-change

unix.stackexchange.com/a/529056