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.
Manufacturers hack it together, flash to device and publish the sources, but dont bother with upstreaming and move on.
Same story as android devices not having updates two years after release.