I've encountered a problem with the bluetooth, but I can't really say it is the fault of the M0, just fishing around for possible solutions.
I have used the AAC codec on the M0 before with bluetooth over-ear headphones and they worked very well. Recently though, I got a true wireless earphone that supports SBC and AAC. It works fine on SBC, but on AAC, it connects and no sound comes out. You can tell that it is trying to play something because the background hiss kind of leaves when I hit play, but there is no music, just an absence of hiss. It almost feels like when my android phone connected in phone audio but not media audio. Anyways, I am still waiting for a response from the earphone makers, but I am wondering if there is any solution or anything I can do on the M0 side of things to push it into working properly.