I can't remember exactly what workaround I've found for this, but a while back I was able to start a screen recording, turn the microphone on, and then do something VoiceOver related to get the phone to record the screen and the mic all while listening to the game via the speakers.
You can't use AirPods, but you can use regular lightning earbuds. However, while recording this appears to be in mono.
I've used a AirPlay mirroring app on my computer before, but I believe the one I use no longer records VoiceOver which is obviously a problem.
Anyone have any solutions or workarounds? I want to continue my Six Ages playthrough on Youtube, however the stutter after a while with the airPlay mirroring just isn't great for Youtube. I'd like to be able to sound as professional as I can, and the way to do that is to record the sound directly. Apple says it was a design feature to have the audio go to the earpiece when recording the Mic due to people in meetings, but why would you screen record a meeting?