Multiple DualShock 4 Controlers detected as one

I've tried to use Qt GamePad with my 4 DS4 controllers.

I've connected 4 Sony DualShock 4 v2 controllers via Bluetooth.

It should detect all gamepads and print events of all of them.

It thinks that only one gamepad has been connected, but I have connected 4 gamepads.

    auto gamepads = QGamepadManager::instance()->connectedGamepads();
    qDebug() << "Number of gamepads:" << gamepads.size();

prints "Number of gamepads: 1"

If I press any button on one of them, it prints a message that button was pressed, but shows the same device ID.
Environment: Ubuntu 19.10, latest Qt version from online installer (5.13.2)

tried

QT_GAMEPAD=sdl2

and

QT_GAMEPAD=evdev

Both resulting in the same issue: all 4 act as if they were 1 gamepad

$ ls /dev/input/js*
/dev/input/js0  /dev/input/js1  /dev/input/js2  /dev/input/js3