And guess what? Those smartphones, cars, etc. are all made by a relatively small number of suppliers on....homogeneous hardware. Samsung, Xiaomi, Motorola, Sony, OnePlus (any other majors?) are pumping out devices running the same stack and writing their own drivers. Can you plug a non-Samsung internal storage device into a Samsung phone? Can you attach a screen from a Samsung device to a Motorola phone? Will a Xiaomi modem work in a Sony phone?

Buy a consumer Walmart PC running Windows and it is expected to be plug and play with nearly any graphics card, USB scanner, printer, etc. I don't think Microsoft gets enough credit for supporting such a huge and varied consumer user base.

For sure, Linux is the core of every Android device and every modern car. But those hardware stacks are homogeneous by manufacturer and there's only a handful of major manufacturers; those devices are carbon copies from a hardware perspective and a manufacturer only has a handful that they support at any given time.