Hello,
The HTTP Live Streaming (HLS) links are not supported as onebox.
What you can do is to use the <video> HTML tag.
For example:
<video controls preload="metadata">
<source src="https://demo.unified-streaming.com/k8s/features/stable/video/tears-of-steel/tears-of-steel.ism/.m3u8" type="application/x-mpegURL" />
</video>
You can use this Insert Video component to insert the <video> tag easily.
From what I see, the HLS support is pretty limited to Android/IOS devices, with no major desktop browser except Safari.
If you want to make it work on a Desktop, you will need a third-party library, such as videojs, and a Theme component to integrate it.