I am experiencing this problem on 5.11.2 running Linux Mint. So it is still there.
Using the following formulation:
QColorDialog dlg(colored->getColor());
dlg.setOption(QColorDialog::DontUseNativeDialog);
dlg.setOption(QColorDialog::ShowAlphaChannel);
dlg.open(this,SLOT(slot_colorChanged(QColor)));
dlg.exec();
First problem: the dialog initializes with color black, not the given color. When pressing OK, the slot is triggered
but the color is always color white, whatever is selected in the dialg. So essentially it does not work at all.
using the formulation
QColor newColor = QColorDialog::getColor(m_color, this, QString(), QColorDialog::DontUseNativeDialog);
does work as was mentioned before