When interacting with a webpage that uses the pressure of the stylus to react differently it will have no effect

When interacting with a webpage that uses the pressure of the stylus to react differently it will have no effect. It will act the same regardless of the pressure applied. This can be reproduced in the example by picking a brush to draw with and then drawing with it, the thickness of the line should change as it draws.

Note that although this reproduces in Qt 5.12.4, you need the patch to get it working generally in Qt Declarative so using Qt 5.12.x is better before 5.12.5 is out.