I spotted a strange thing. I have a webcam (a4tech p-635, pretty old) which is not recognized by any UWP app, like modern skype. With standard apps, everything works like a charm. I will say even more; same code in Qt compiled with MinGW can handle this camera, but compiled as UWP, can't detect her.
Have you any ideas? I can't find anything which could be a cause. Thanks.
That is most likely caused by the camera drivers. UWP app API is great at abstracting devices and access them via the simple API, but if the webcamera is not recognized, it must be that the drivers for the camera are not providing the right interface that UWP can use.
Please check if there are newer drivers available and if you cannot install some generic driver that would make the camera work.