> I think software updating itself is sort of a windows mentality.
Yes it's definitely a mentality of "the apps are separate from the OS" at least, which is basically every OS except Linux/Unixes with central package managers. Even on a Debian or Ubuntu system, I'd be using dozens of non-packaged applications though (Be they locally compiled from github, or flatpacks or whatever).
Most other operating systems (linux, macos, ios, etc) update through an os-wide mechanism.
Debian already has apt and that downloads a list of package names and versions from each repo and what is on the system is generally hidden. If the user asks to install a package, then the user has opted-in to download and install that package/dependencies. Also the packages can come from a variety of caches and mirrors.