Swift - AVAudioEngine fails to default to system output - swift

Question

I try to use AVAudioEngine to playback audio. Here is my code stripped down to the minimum:
import AVKit
let audioEngine = AVAudioEngine()
let audioPlayer = AVAudioPlayerNode()
let mainMixer = audioEngine.mainMixerNode
/*
let outputNode: AVAudioOutputNode = audioEngine.outputNode
let outputUnit: AudioUnit = outputNode.audioUnit!
var outputDeviceID: AudioDeviceID = 240 // Magic Numbers: 246 Line out, Built-in Speaker: 240 - these will be different on other computers
AudioUnitSetProperty(outputUnit, kAudioOutputUnitProperty_CurrentDevice, kAudioUnitScope_Global, 0, &outputDeviceID, UInt32(MemoryLayout<AudioDeviceID>.size))
*/
audioEngine.attach(audioPlayer)
audioEngine.connect(audioPlayer, to: audioEngine.mainMixerNode, format: nil)
try! audioEngine.start()
let kPlaybacklFileLocation = "/System/Library/Sounds/Submarine.aiff"
let audioFileURL = CFURLCreateWithFileSystemPath(kCFAllocatorDefault, kPlaybacklFileLocation as CFString, .cfurlposixPathStyle, false)
let audiofile = try! AVAudioFile(forReading: audioFileURL! as URL)
audioPlayer.scheduleFile(audiofile, at: nil)
audioPlayer.play()
The code runs in an XCode 11 Playground and should output the "Submarine" alert found in the system sounds, or you may direct it to any other soundfile.
I have a macbook pro mid 2012 (non retina) running on Mojave and the code runs as expected.
However, on my 2018 Mac mini, also running Mojave, the playground runs without errors but no sound is heard. Only after I set the outputNode explicitly to a specific output (as found in the system preferences) by adding the code in comments it works.
Anyway, this would not be a viable solution, as the output so would be bound to the specified port. On my macbook, where the code works without the commented part, the output will be rerouted to whatever I specify in the system panel whithout even having to restart XCode.
I retreived the outputDeviceID 240 using AudioObjectGetPropertyData, the code needed is to verbose to show, but it is noteworthy that besides the physical outputs "BuiltInHeadphoneOutputDevice" and "BuiltInSpeakerDevice" there is also an "CADefaultDeviceAggregate-2576-0".
Also noteworthy is that the device list differs from the list I get using AudioComponentFindNext which only gives me entries like "AudioDeviceOutput" and "DefaultOutputUnit".
I would expect that the AVAudioEnginewould use the AUHAL to be routed to the default unit.
So why does the same code in the same XCode version and the same OS runs fine on one machine and not the other?
What do I have do change within the code to guarantee that on any machine the audio goes to the output which is set in the system preferences?
Some further considerations:
The Mac mini has the T2 security chip which puts more restraints to what XCode may have access to
I have no paid developer account, some entitlements need certificates I therefore cannot grant
I have some virtual outputs (blackhole, soundflower) installed on the mini, but system output is set to either built in speakers or headphones/lineOut