See the attached example.

If you try to access url "https://www.imdb.com/title/tt3183660", any desktop browser would redirect you to http version of imdb.com which WebEngineView does not do. It does work the opposite way (http://twitter.com redirects to https://twitter.com) though. I believe it might work this way by security reasons, but then there should be a setting which would allow to choose whether WebEngineView should redirect from https to http automatically or not (all major desktop browser do redirect, so I think WebEngineView should do that by default as well).

When you try to access a link redirecting from https to http, WebEngineView emits loadingChanged signal and loadRequest.status is LoadStoppedStatus which is not documented, I opened a separate issue for that: QTBUG-57636
http://doc.qt.io/qt-5/qml-qtwebengine-webengineview.html#LoadStatus-prop