There are still ways to download YouTube videos. For the Mac, ClipGrab works and is safe. There is a good command line tool for all platforms: yt-dlp It's open source.
If you create a new custom formatting tag, you can embed a video into a custom slide, by providing the video id, which you get from the share button below a video. Choose EMBED and copy the URL.
In OpenLP, create a new formatting tag (say, yt) and use the EMBED URL you just got as the model for the tag start and end.
For our last live stream, this is
<iframe width="560" height="315" src="https://www.youtube.com/embed/xxuWyuo-Mt4?si=o_1qAJ1rmr4vGcXJ" title="YouTube video player" frameborder="0" allow="accelerometer; autoplay; clipboard-write; encrypted-media; gyroscope; picture-in-picture; web-share" referrerpolicy="strict-origin-when-cross-origin" allowfullscreen></iframe>
the width and height are too small for our OpenLP screen, so I made the Start HTML this:
<iframe width="1280" height="720" src="https://www.youtube.com/embed/
and the End HTML this:
" title="Video" frameborder="0" allow="accelerometer; autoplay; clipboard-write; encrypted-media; gyroscope; picture-in-picture; web-share" referrerpolicy="strict-origin-when-cross-origin" allowfullscreen></iframe>
The custom slide gets the video ID and the ?si= parameter
{yt}xxuWyuo-Mt4?si=E8_MheUAVcI9Nf-C{/yt}
If you want the video to show full screen, choose a theme that uses the whole screen, or make the height and width smaller to fit your theme.
You may have to manually click the start button on the video ON YOUR PROJECTOR, or click anywhere really. The autoplay in the embed code doesn't always work. That's the drawback; you can't just click in the live panel. I'm sure this has been explained in the forum before, but YouTube keeps changing things up.