Hey there
jerryy2345 many thanks for your reply, I really appreciate your comments but you have misunderstood my questions:
Airplay Mirroring is actually "Screen" mirroring (to my Apple TV's which is not working) whereas you have confused this with Just AIRPLAY - which is audio only and to which I have working. Yes I do have audio out from my MB - but I don't need it.
I NEED audio out of my Display Port, let me explain, and forgive me if your from the US and don't know what Sky Q is (cable, HBO etc) !
My brief was that I needed a 4K monitor with 1 x input for an apple TV (HDMI) and 1 x input for my Sky Q Box (HDMI) and another input somehow from my Hackintosh - to make things harder the monitor also needed to be white!!
After months of scouring the internet with no luck I went to the US on vacation, strolled into a FRYs electronics and found a WHITE LG 4K monitor with 2 x HDMIs and 1 x DISPLAY port - bingo. Even better it had an audio out jack that meant the monitor acts as a music source selector or "mixer" for the audio - whatever's on the screen comes out the audio jack on my monitor and into my speaker system. On windows this all works great as there's of course an RX 460 driver.
But in MacOS with no audio being fed into the DP my whole plan comes crashing down around me as the monitor is key to my audio distribution. My audio has only 1 x wired input or Bluetooth (tried latter its laggy).
The fact that the monitor was to big to buy and take home on the plane, and that they don't sell them in the UK is another story that's best left for another time - but after all this careful planning see why I must have audio thru my DP?