Yes, I was trying to get the Camera working in iOS 11.2.6 without success:
...
public ngAfterViewInit() {
    const constraints = {
      audio: false,
      video: {
        width: { min: 1024, ideal: 1280, max: 1920 },
        height: { min: 776, ideal: 720, max: 1080 },
        facingMode: 'environment'
      }
    };
    if (navigator.mediaDevices && navigator.mediaDevices.getUserMedia) {
      navigator.mediaDevices.getUserMedia(constraints).then(stream => {
        this.video.nativeElement.src = window.URL.createObjectURL(stream);
        this.stream = stream;
        this.video.nativeElement.play();
      }).catch(function(err) {
        this.logger.error(err.name + ': ' + err.message);
      });
    } else {
      this.logger.error('Your browser does not support the mediaDevices API');
    }
  }
}
...
E.g., navigator.mediaDevices.getUserMedia() is undefined 
So then I switched to using:
  <input type="file" ... >
Which allowed me to access the device’s photo library but not the camera (of a device running (iOS 11.2.6).
iOS 11.3 allows access the device’s camera and the photo library via the <input type="file"> element.
But, navigator.mediaDevices.getUserMedia() is still undefined.
See: https://medium.com/@firt/progressive-web-apps-on-ios-are-here-d00430dee3a7