What kind of source are you looking for. This is about hundreds of changes that all build up to a more locked down experience.

iOS has always been locked down.

MacOS now won't run unsigned software. Mac Pros will brick if you replace the SSD with another genuine SSD.

Safety net on android makes it harder to use root. There is an API to block screenshots. Security changes in Android 11 break termux and all other bash apps.

Windows tried RT and the S version but it doesn't seem to be replacing the regular one yet.