[Qtwebengine] Any way to debug seemingly not working Pepper Flash plugin?

[Herman van Hazendonk]

I'm trying to get Pepper Flash Plugin working on our QtWebEngine 5.6+ 
that's compiled using the meta-qt5 layer 
(https://github.com/meta-qt5/meta-qt5)

I made sure I have enable_plugins set properly during the build & 
enabled the plugins setting in our WebEngineView, just it seems that 
Flash support is not working when I place the libpepflashplugin.so in 
the locations as indicated. I tried:

/usr/lib/pepperflashplugin-nonfree/libpepflashplayer.so
/usr/lib/PepperFlash/libpepflashplayer.so
/usr/lib/qt5/plugins/ppapi/libpepflashplayer.so

Any ideas how I can see if the plugin is loaded properly? Is there 
something equivalent to Chrome's: chrome://plugins or Firefox' 
about:plugins available?

Any suggestions for debugging this would be welcome!

Thanks,
Herman