Car manufacturers have money. They can and will lobby the monopoly status quo.

Money talks. I know it's hard when you want that nice car, but considering the above, the only way is just not buying the car with software lock-in. Only this stimulus can have some effect.

There is. You can swap out the head unit with an aftermarket one.

Most modern cars I've seen don't seem to have old DIN sized head units these days.

You used to be able to. It’s becoming increasingly difficult.

Many cars can be modified even now with increasingly integrated entertainment systems. Beatsonic or its various Chinese copies are an example of this, it’s a box that hijacks the video stream and lets you add CarPlay functionality and stuff.