build

What? Every single one of them does. Just switch to the UEFI Setup and disable Secure Boot. Note that I'm talking about Arm 64-bit Windows, and not the earlier Windows RT which is dead. Details for Linux for the best-supported Windows on arm64 laptops on that front at: https://github.com/aarch64-laptops/build

See the recent announcement of Arm SystemReady SR and ES, which is a standard mandating UEFI across the board. Yes, Secure Boot can be disabled on Windows on Arm systems in the same way as Windows on x86_64 systems. For Windows on Arm laptops, you cannot quite use upstream kernels at this point w/ full functionality, see https://github.com/aarch64-laptops/build. (being rebased continuously). For other Arm machines, like servers, you can just use regular kernels though. And over custom partitions and other things, it's just UEFI now, the firmware itself is in a secondary SPI flash or an UFS namespace. * you might always need to run a script to extract firmware for the GPU/modem and such, which are OEM-signed on Qualcomm Windows/arm64 devices. That firmware is then put to /lib/firmware/.

The Arm laptop community for these higher-end cores in laptops is currently active here: https://github.com/aarch64-laptops/build + You can install your own OS. + Mainline Linux boots, with some caveats. + There is an Ubuntu 18.04 patched installer that works as expected, but support for the platforms isn't in the main distro installers yet.

One correction: Unlocked boot loaders are still present. All the platforms that I have seen that support Windows on Arm have boot loaders that can be unlocked. This is probably the best place to follow machines that have unlocked boot loaders, as currently Linux enablement requires it: https://github.com/aarch64-laptops/build

https://github.com/aarch64-laptops/build is where the instructions to run Linux on Windows/arm64 devices. Note however that the Pro X isn't quite supported yet.