Same story here. Simulators with iOS 12.2 crash and burn when initializing audio on [AudioHAL_Client] HALB_IOBufferManager.cpp:226:GetIOBuffer: HALB_IOBufferManager::GetIOBuffer: the stream index is out of range just like OP stated. I'm on Big Sur 11.6 and XCode 12.5.1 I downloaded the iOS 14.3 runtime and now it works. Not an acceptable solution and it's been 9 months since the OP. C'mon Apple, let's go.