The first principle, is when I have a thing (computer, car, toaster), I
have the thing. It’s mine. I control it, I can have it repaired wherever, I can resell it, and if I have the skill, maybe even tweak it. But most importantly the thing serves
me, not the corporation that sold it to me.
If the thing is a general purpose computer that can run arbitrary software (and I’d be tempted to include anything that can be remotely updated as "software", so this would include Tesla’s firmware), then I should be able to run my software instead. That’s the true test of whether I truly own my computing device.
Before we even get to Free Software, we need documented hardware architectures.