[zanny]

If the bootloader is unlocked / fastboot can write to the bootloader / etc you can put whatever code on your phone you want to run.

The problem is the hardware is undocumented and the shipped drivers are proprietary so you would need to reverse engineer support for everything from the chipset to the modem to the display adapter.

So you can go throw a Debian Arm image in place of a system partition on many Android phones... it just won't boot.

[dmitrygr]

That isn't true. It will actually boot. In fact, you will even have unaccelerated graphics. Depending on the phone, you will probably have working Bluetooth. WiFi will work if you copy the firmware image from the original Android installation. Touch screen will work perfectly fine. Power management and thermal management are going to be a lot of work. Graphics acceleration is unlikely

[rsync]

"So you can go throw a Debian Arm image in place of a system partition on many Android phones... it just won't boot."

Won't even boot ?

I would expect that peripherals and radios and so on would be out of reach due to hardware/drivers but my expectation was that you could boot and get serial comms somehow ... as unusable as that would be ...