On Ubuntu 22.04 the microphone device is captured before recording starts

 #include "mainwindow.h"
#include "./ui_mainwindow.h"

#include <QMediaCaptureSession>
#include <QAudioInput>

MainWindow::MainWindow(QWidget *parent)
    : QMainWindow(parent)
    , ui(new Ui::MainWindow)
{
    ui->setupUi(this);

    auto captureSesstion = new QMediaCaptureSession;

    // After this line, a microphone usage indicator will appear
    captureSesstion->setAudioInput(new QAudioInput(this));
}

MainWindow::~MainWindow()
{
    delete ui;
}

captureSesstion->setAudioInput(new QAudioInput(this));