I recently got a Orange PI 3 an dI am playing with it.
First thing I did was run Android 7 image from SD Card and it installed Android on EMMC.
After finally switching from chinese to english, I was able to play with it.
Now I want to boot from SD Card again - and in best case remove Android from EMMC.
also for now android have best hardware support. if you want to boot linux from EMMC then armbian distro is able to do that, i was not able to make hdmi to work.