It would be great to share some info about your issue with webos 4...

[nyomen]

Can you please tell where and what is the problem, to give some initial idea about what's the issue with webos4, so other people will also have the possibility to dig into that.
Thanks.

I guess you also aren't a big fan of bug descriptions like:
"it's not working because it's not working, no matter what, I have tried everything it's not working, because see it's not working."
Don't be that guy.

[aabytt]

Qml webos apps use PunchThrough element to play video on top of graphic layers (system UI, apps, etc).
Webos 4 seems to miss support of this element. That's why video is being played at the bottom layer and is not visible.

There is a declaration of app type as screensaver
You can try a different app type. This may help to display the video properly but the app will no longer automatically act as screensaver.
There is a thread on discord openlgtv server where can post your ideas on this problem.