xenial-mainline-edge vs xenial-hybris-edge: what's the difference?

[YamiYukiSenpai]

So what's the difference between the 2?

[dobey]

The mainline rootfs is for devices which use upstream Linux kernel with open source drivers on standard GNU ABI, rather than Android. So, for PinePhone/Librem 5/RPi.

The hybris rootfs is for devices which require Android kernel and its bionic ABI (hybris is for binding to the Android HAL from within Linux).

If you're porting a device, you almost certainly need the hybris version.