For info I found also another alternative:

... import QtQuick.Controls 2.12 import QtQuick.Controls.Material.impl 2.12 ... ProgressBar { ... id: pbProgress contentItem: ProgressBarImpl { implicitHeight: pbProgress.height anchors.fill: parent anchors.margins: 0 scale: pbProgress.mirrored ? -1 : 1 progress: pbProgress.position indeterminate: pbProgress.visible && pbProgress.indeterminate color: "#5014ad" } ... }