QWebEngineView to view local pdf at certain page

kazaak

I set a url to the webengineview and it works fine but the page argument is ignored:

QUrl url(QUrl::fromLocal(pdfPath));
url.setFragment("page=3")
webView.setUrl(url);

I've tried this with online pdfs as well. I see this in the application output:

[5852:7404:0423/101833.779:ERROR:extension_function_dispatcher.cc(487)] Permission denied for metricsPrivate.recordValue
js: Unchecked runtime.lastError: Access to extension API denied.
js: Uncaught (in promise) TypeError: Cannot read property 'getStrings' of undefined
js: Uncaught Error: Assertion failed

Is this just not supported? I'm using MSVC 2019 and Qt 5.15.2

edit:
I've also tried via js:

webView->page()->runJavaScript(QString("window.viewer.viewport_.goToPage(3)"));

and received this message:
js: Uncaught TypeError: Cannot read property 'viewport_' of null

on the loadFinished(bool ok) slot I used a single shot timer which is sometimes needed when js is loading but even up to 5 seconds I still get the same message