The multimedia-class doc is critical as developers port from Qt 5 to 6.

One missing function is referred to in a couple of places, such as here. You'll find this statement:

you can check if the device supports it with isFormatSupported(), or fetch a supported format that is as close as possible to the format with nearestFormat()

The nearestFormat() function no longer exists.

Another reference is here. The comment in the code says it will try to find the nearest format, but the line that used to attempt to do so (by calling the above-mentioned, now-nonexistent function) has been deleted. So this entire piece of code is useless:

QAudioDevice info = QMediaDevices::defaultAudioInput();
if (!info.isFormatSupported(format))

{     qWarning() << "Default format not supported, trying to use the nearest."; }