How can I achieve smooth drawing in QT similar to Onenote or Goodnotes?

Question

I am trying to create an inking mechanic like the one in Onenote or goodnotes using QT. The idea is creating a simple white canvas and a drawing mechanic. I've actually achieved these both, but the lines I draw with the app are too pixelated and not smooth.

Therefore I tried to use smoothing methods of QTPainter library.

void Canvas::penSettings() {
    painter.setRenderHint(QPainter::Antialiasing, true);
    painter.setPen(QPen(Qt::blue, 10, Qt::SolidLine, Qt::RoundCap, Qt::RoundJoin));
}

Image (left one is QT right one is Onenote):

As shown in the image, it didn't turn out as I expected, and now I find myself stuck with these questions: Are Qt libraries enough to achieve this, or should I consider using other libraries like OpenGL or Skia? Do I need to create custom drawing algorithms, or is the issue arising due to antialiasing?