A2DP failing to appear in the list or refusing to set is a longstanding problem that has occurred well before the introduction of gdm. It's one of the things we tried to fix in xenial recently but I know it can still occur sometimes even in artful.
How I experience this bug however is that the Bluetooth device is shown as connected but upon login there is no corresponding audio device.
I think you might have two different bugs...
A2DP failing to appear in the list or refusing to set is a longstanding problem that has occurred well before the introduction of gdm. It's one of the things we tried to fix in xenial recently but I know it can still occur sometimes even in artful.
How I experience this bug however is that the Bluetooth device is shown as connected but upon login there is no corresponding audio device.