The problem isn't support for the ARM architecture in general, it's the support for this particular board.
Other boards like the Raspberry Pi and many boards based on Rockchip SoCs have most of the necessary support mainlined, so the experience is quite painless. Many are starting to get support for UEFI as well.
Of course it is not. That's why almost every ARM board comes with it's own distro, sometimes bootloader and kernel version. Because "it is supported". /s