Do you need to turn on the torch by itself or turn on the flash while opening the camera?
If you are looking for turning on the flash while opening the camera, we have the sample that's called Camera Dialog, that would allow you to adjust the setting of the flash while taking picture or video.
But if you are looking to turn on/off the torch by itself, Qt has a Torch QML type that is supposed to do this, but it does not seem to work on my testing, and also based on the bug report, [QTBUG-79274] iOS Torch does not work, quirk with getting it working - Qt Bug Tracker
I have also tried this https://doc.qt.io/qt-5/qml-qtmultimedia-torch.html but did not work for me as well
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