I still also use Fabien Coeurjoly's OWB YouTube Scripts specifically the YT script file, (which is actually the YouTube HTML5 Converter script), also the EZDownload and Fullscreen Fix Scripts that you can still download from his website, to access YouTube files via the right-context menu option which still works correctly - AFAIK, and is how it works for me, which is activated once you install them into OWB's Scripts folder, then you just start OWB and ... open a YouTube page, and then the video needs to be left-clicked on the play arrowhead, then you should see, when you right-click over a running video file, that's not paused, or waiting to be played, so you'll first of all see the initial You Tube context menu, then right click again, and you should see the OWB context menu with options to Pause, Mute, Control, Loop, Switch to Fullscreen, Copy Media Location, Open Media in New Window ..., Download Media, or Inspect Element. There should also be a small squarish grey background window with a few icons in it with the heading 'You Tube Download', and usually these days it has a 'Error Alert' message below that - which you can ignore. I usually download the video and play it after it's fully downloaded, though the video usually plays in OWB, but with some/limited 'juddering'.

Not sure if this is of any use, but thought I'd mention it anyway, and hopefully it will be.