an idea by ldevulder
The Khadas VIM (http://khadas.com/vim/) is an arm64 DIY Set-Top-Box based on Amlogic P212 reference board that use S905X SoC. As Odroid-C2 (based on S905 SoC) is in the mainline U-boot, it should be possible to adapt it for the Khadas VIM (of course a lot of work are needed!).
a project by aplanas
The Gameshell is a small game console based on AllWinner R16 (Cortex-A7, IIRC the same CPU that the RPi2). Currently is supporting Debian, and some community member ported ArchLinux on it. The goal of the project is to port the openSUSE MicroOS distribution into the device, providing a transactional upgrade process for a canonical IoT architecture. In the process I expect to learn about ARM7, uBoot and some kernel hacking.