all appliances used to come with schematics and repair manuals, there was no prevention of modification or repair. We're talking cars, washing machines, dryers, radios etc.

Separate from computers and phones locking down devices is a much wider issue, usually it is only implemented to reduce liability of the manufacturer or to allow for planned obsolescence.

> They perform the specific functions that they were programmed to perform

That's the thing. You may have bought a device that was meant to perform a task but after some time the company decides that now it should do a different task. I think that's what stops making you the owner. You can't really choose what to do with it.

You can absolutely install Linux on a Mac. Back before Apple made custom CPUs they supported and even advertised installing Windows.

https://en.wikipedia.org/wiki/Boot_Camp_(software)

You _can_ run other OSes on Macbooks. They're not locked in at all, it's simply that the drivers aren't open source and the hardware is undocumented, but with enough effort (e.g. Asahi) you can run technically anything on it.

>which will result in fragmentation.

Why? And how does that bother you?