PROCESSOR-SDK-AM335X: Error running QtWebengine

I was wondering if anyone here has had success building Qt 5.8 or 5.9.1 against SDK 3.03.00.04 and then running a QtWebEngine application.

My team has done the Qt build, but when trying a trivial QtWebEngine app (see below), we get the following output.

This plugin does not support createPlatformOpenGLContext!
Could not find QtWebEngineProcess

We think the first error ("plugin does not support") message is not the cause of the second error message ("coult not find") as we see that same first error message with older versions of Qt and when not using QtWebEngine from the 5.8/5.9 versions of Qt (e.g. when using plain old Qt widgets) yet the app still runs fine.

It's only when we go to 5.8/5.9 version of QtWebEngine that we get the second errror message ("Could not find QtWebEngineProcess") and indeed, that secondary QtWebEngineProcess does not get started and our application exits with error.

We're working with Qt tech support about to fix this (including the first error message), but they respond very slowly, so I was hoping to at least see if anyone here has actually managed to get QtWebEngine going with 5.8/5.9.

Thanks in advance.

Here is the test program we're using:

#include <QApplication>
#include <QWebEngineSettings>
#include <QWebEngineHistory>
#include <QWebEngineHistoryItem>
#include <QWebEnginePage>
#include <QWebEngineView>
#include <QtWebEngine/qtwebengineglobal.h>

int main(int argc, char *argv[])
{
    QApplication app(argc, argv);
    QtWebEngine::initialize();
    QWebEngineView view;
    view.resize(600, 600);

    if (argc == 1)
    {
        view.setUrl(QUrl(QStringLiteral("http://localhost")));
    }
    else
    {
        char *p = argv[1];
        view.setUrl(QUrl(p));
    }

    view.show();
    return app.exec();
}