I used the code from Nikolay answer https://jsfiddle.net/makhalin/nzw5tv1q/ on my Ionic - Angular PWA (I put it on a custom.js file and imported it on angular.json). It's working great if I open it in Chrome or Edge on Android but if I install it as a PWA it works the first time, then stops working.

Is there anything I must do to make it work as a PWA?

//have a console on mobile
const consoleOutput = document.getElementById("console");
const log = function (msg) {
  consoleOutput.innerText = `${consoleOutput.innerText}\n${msg}`;
  console.log(msg);
}

//Test browser support
const SUPPORTS_MEDIA_DEVICES = 'mediaDevices' in navigator;

if (SUPPORTS_MEDIA_DEVICES) {
  //Get the environment camera (usually the second one)
  navigator.mediaDevices.enumerateDevices().then(devices => {

    const cameras = devices.filter((device) => device.kind === 'videoinput');

    if (cameras.length === 0) {
      log('No camera found on this device.');
    }
    // Create stream and get video track
    navigator.mediaDevices.getUserMedia({
      video: {
        facingMode: 'environment',
      }
    }).then(stream => {
      const track = stream.getVideoTracks()[0];

      //Create image capture object and get camera capabilities
      const imageCapture = new ImageCapture(track)
      imageCapture.getPhotoCapabilities().then(capabilities => {
        //let there be light!
        const btn = document.querySelector('.switch');
        const torchSupported = !!capabilities.torch || (
          'fillLightMode' in capabilities &&
          capabilities.fillLightMode.length != 0 &&
          capabilities.fillLightMode != 'none'
        );

        if (torchSupported) {
          let torch = false;
          btn.addEventListener('click', function (e) {
            try {
              track.applyConstraints({
                advanced: [{
                  torch: (torch = !torch)
                }]
              });
            } catch (err) {
              log(err);
            }
          });
        } else {
          log("No torch found");
        }
      }).catch(log);
    }).catch(log);
  }).catch(log);

  //The light will be on as long the track exists
}