"Format as Internal Storage" option no longer available
It seems like manufacturers are removing the "Format as Internal" feature on newer phones. Perhaps because it's in their interest to force us to upgrade our devices after running into memory frustrations.

So after a long and frustrating process, this eventually method worked for me. I had to make two alterations:


I used the MTK ADB driver instead of the one linked in the guide. This depends on your chip type, there's no harm in trying both if you don't know which to pick. Just that your phone might not show up on step 7.
On step 8, the fourth command adb shell sm partition disk:179,64 private might give you a java exception error. I had to use my result from the first command adb shell sm list-disks which was something like disk:179,124. The author neglects to mention that this may vary for your device.


With a bit of patience this should work for you too. If I missed anything, search the comments of the article, another person's experience might give you a clue.