auto inputDevices = QMediaDevices::audioInputs();
    auto input = QMediaDevices::defaultAudioInput();

    qDebug() << "Default:" << input.description() << "\nAll available:";
    for (const auto &inputdevice : inputDevices) {
         qDebug().noquote() << "Description:" << inputdevice.description()
                                          << "is default:" << inputdevice.isDefault()
                                          << "id:" << inputdevice.id();
    }

Default: "Family 17h (Models 10h-1fh) HD Audio Controller Analog Stereo" 
All available:
Description: Family 17h (Models 10h-1fh) HD Audio Controller Analog Stereo is default: false id: alsa_input.pci-0000_05_00.6.analog-stereo
Description: Razer Seiren Mini Mono is default: false id: alsa_input.usb-Razer_Inc_Razer_Seiren_Mini_UC2119L03203407-00.mono-fallback