How to acquire audio from the input jack using the JavaScript Web Audio API on iOS/Safari?

I am writing a JavaScript web app that is meant to read an input audio stream being captured via the audio input jack on a mobile device. The following snippet shows how I get the input source on my JS code:

return navigator.mediaDevices.getUserMedia({
    audio: {
      echoCancellation: false,
      autoGainControl: false,
      noiseSuppression: false,
      latency: 0
    }
  })

However, I’m only able to get audio input from the microphone.

Is there any way that I can select other audio input sources in an iOS mobile device running this web app via Safari?

(note: I’m using iOS 14.8.1 on an iPhone 12 mini).