It’s true that the camera feature is not listed as unsupported in web apps. I suppose that’s an indication it should work.
But you’re right, it doesn’t. If I preview this on my iPhone in Thunkable Live, it works as expected showing the camera “recording” view and the image I captured:
But if I publish it as a web app and view it in Chrome on my iPhone, nothing happens when I tap the Take Photo button.
You can submit this as a bug on GitHub: https://docs.thunkable.com/bugs-and-feature-requests.