Numpad shortcuts does not work for Linux

import QtQuick 2.15
import QtQuick.Window 2.15

Window {
    width: 640
    height: 480
    visible: true

    Shortcut {
        sequence: "Num++"

        onActivated: console.info(sequence)
    }

    Shortcut {
        sequence: "Num+Left"

        onActivated: console.info(sequence)
    }

    Shortcut {
        sequence: "Num+4"

        onActivated: console.info(sequence)
    }
}