What counts as success? There are two aspects to consider.
Getting the Unity8 shell and some core apps running
Also chosing some "phone" hardware and adding support
Unity8 has yet to be ported to distros beyond Ubuntu, so goal 1 would be easiest on Ubuntu. On the other hand, having it running on Raspbian or as a Snap would generate interest.
Goal 2 will surely need kernel work and is an area that will be problematic to integrate into Ubuntu Core & snapd.
@jonius Ok let me explain with a screenshot - this one is from the old boot layout, where android system is inside ubuntu.img and system.img is a hardlink to ubuntu.img, so please forgive the sizes of the files. This WILL change with Halium):
partition BOOT: Contains initrd system with kernel and the usual initrd helpers
partition DATA: ext4 formatted, contains:
ubuntu.img is the read-only root filesystem
system.img contains the Android LXC container. This will not be needed at all for Raspberry
folder user-data: Contains all user data from the home dir
folder system-data:Contains system settings like WiFi, network, future printing, etc.
So, if you manage to boot the raspberry image, your bootloader basically needs to follow the steps of https://github.com/ubports/ubports-boot and its initrd workflow. Specifically, see this init: https://github.com/ubports/ubports-boot/blob/master/initramfs/init