The guide should also mention respecting copyright. It's important to note that distributing or using such links for illegal purposes is not allowed.
But getting the m3u8 link from a legitimate source involves knowing the URL structure of the streaming service. For example, some platforms expose the HLS URL in the page source. However, this requires technical know-how and might still be against the service's terms.
So the guide should first clarify the legal options: check if BBC Earth is available on Freeview or via the BBC Player, or via international partnerships depending on the region. If they have a subscription to a service that provides BBC Earth, they could use a streaming app and then use a tool like VLC to open the stream.