I’m sorry if this sounds like a stupid question but why won’t android just straight up run like Linux distros that almost run on any computer? Why does each model under each manufacturers require separate maintainors seperately? Aren’t they running like almost similar hardware like processors from Qualcomm, mediatek, Exynos, etc? Why hasn’t there been a single android os that is compatible with all the device?
Mainly two reasons, one about architecture, and one about vendors
In the PC world, the entire ecosystem is designed to be modular, and people expect to be able to put windows/Linux on any pc and have it work despite the manufacturer. The kernel just wakes up on one of the cores, figures out the CPU, wakes the rest of the cores, and from there it figures out the rest of the computer. By contrast arm systems are tightly integrated, each SoC is unique and there’s no way to figure out the rest of the system, the kernel wakes up on one of the cores, reads out what SoC this is, and mostly has to already know the chip and any additional hardware connected to it.
But, sure, there are only so many SoCs (kinda), and displays, cameras, and touchscreens are mostly similar, you are bound to find a way to tell the kernel what hardware is running on and have it work, right? Except a lot of phone hardware is proprietary (duh) and requires bespoke proprietary drivers, google pretends to encourage vendors to submit their drivers upstream, but this doesn’t really happen. Now, if you are familiar with running external drivers on Linux, you probably know how picky the kernel is in what to load, but android’s kernel is specifically modified to be less picky, to allow vendors more slack. Mind you, the API is not more stable, the kernel is just less picky.
Bonus: running Linux on arm laptops is indeed proving kind of a challenge (nothing impossible, but resources are limited), that’s because they are built like a mobile phone.