I have successfully built and booted this Android6 source on the M64. If you are familiar with Allwinner build procedures you will be able to build it. This is not a normal Linux distribution, it does not build like a normal Linux distribution. You have to use the Allwinner build procedures.
I'm going to put it up on gitlab in a form were developers can use it. I'll include some instructions on how to build it. You probably want the userdebug build so that you'll get a serial console.