iOS Speech Error on Mobile Simulator (Error fetching voices)

I'm writing a simple app for iOS and I'd like to be able to do some text to speech in it. I have a basic audio manager class with a "speak" function:

import Foundation
import AVFoundation

class AudioManager {
    static let shared = AudioManager() 
    
    var audioPlayer: AVAudioPlayer?
    var isPlaying: Bool {
        return audioPlayer?.isPlaying ?? false
    }
    var playbackPosition: TimeInterval = 0
    
    func playSound(named name: String) {
        guard let url = Bundle.main.url(forResource: name, withExtension: "mp3") else {
            print("Sound file not found")
            return
        }
        
        do {
            if audioPlayer == nil || !isPlaying {
                audioPlayer = try AVAudioPlayer(contentsOf: url)
                audioPlayer?.currentTime = playbackPosition
                audioPlayer?.prepareToPlay()
                audioPlayer?.play()
            } else {
                print("Sound is already playing")
            }
        } catch {
            print("Error playing sound: \(error.localizedDescription)")
        }
    }
    
    func stopSound() {
        if let player = audioPlayer {
            playbackPosition = player.currentTime
            player.stop()
        }
    }
    
    func speak(text: String) {
        let synthesizer = AVSpeechSynthesizer()
        let utterance = AVSpeechUtterance(string: text)
        utterance.voice = AVSpeechSynthesisVoice(language: "en-GB")
        synthesizer.speak(utterance)
    }
}

And my app shows text in a ScrollView:

  ScrollView {
      Text(self.description)
          .padding()
          .foregroundColor(.black)
          .font(.headline)
          .background(Color.gray.opacity(0))
  }.onAppear {
      AudioManager.shared.speak(text: self.description)
  }

However, the text doesn't get read out (in the simulator). I see some output in the console:

Error fetching voices: Swift.DecodingError.dataCorrupted(Swift.DecodingError.Context(codingPath: [], debugDescription: "Invalid container metadata for _UnkeyedDecodingContainer, found keyedGraphEncodingNodeID", underlyingError: nil)). Using fallback voices.

I'm probably doing something wrong here, but not sure what.