Microsoft is killing Office 2021 in October to push you onto Microsoft 365, how to fight back
(www.windowslatest.com)
it isn't being "killed", it's just EOL, on schedule. the death-blow comes if windows version has a similar digital certificate expiry baked-in like office mac does. which would be a first on windows, because old (even really old) office versions do still work--just don't get security fixes once EOL.