Let me just add that if you right-click in a Chrome browser window, the context menu is quite different depending on whether you right-click on a link ("Open Link in New Tab," etc), on an image ("Save Image as..." etc), on open text ("Back", "Reload" etc), even different again on an image that is inside a link.
So the browser code itself certainly has all the details of the target under a right-click. With QWebPage that information is available. I hope that it is available from QWebEnginePage and that I have just overlooked it.