Now try running your own build of Linux on a phone, or similar devices. It most probably won't work, because the likes of Qualcomm, Mediatek, Samsung, Huawei, A

Now try running your own build of Linux on a phone, or similar devices. It most probably won't work, because the likes of Qualcomm, Mediatek, Samsung, Huawei, Apple have locked down the hardware so you can only boot digitally signed firmware that matches public keys fused into the device. And that firmware does the same when loading the rest of the OS.