Well now it's back...
Thanks to some legwork (no pun intended) by @longshanks197 we now have a workable solution.
I have created this patch to fix the issue by patching the boot image and replacing sm.jar in system.
This will enable the adoptable storage feature in Settings>Storage
This should work for pretty much any Samsung device running Marshmallow
I advise making a backup with TWRP before proceeding.
NOTE: Due to Samsung's modifications the combined storage capacity may show as incorrect, ignore this and pay attention to the separate internal and external capacity which is correct.
Copy the zip below to your device then install with TWRP.
For information how to enable adoptable storage see the guide below:
This may also be worth a read for more info:
DONATE ME HERE IF YOU WANT TO BUY ME A BEER OR HIT THE THANKS BUTTON IF I HELPED YOU