Google has removed the Google search help documents for the live coverage carousel, which was something Google launched in 2016 as a pilot launch. John Mueller from Google said "It's currently still in very limited availability, so it doesn't make sense to have the docs public just yet."
Barry Adams noticed it went away and asked about it on Twitter:
It's currently still in very limited availability, so it doesn't make sense to have the docs public just yet. (I believe they've been like this for quite some time now.)
— 🍌 John 🍌 (@JohnMu) December 11, 2019
The interest form is still live for submitting to that but the help docs are missing.
I know the Google team has been cleaning up their help docs a lot over the past year or so, so maybe Google moved the non-public features to a private area?
You can learn more about this live coverage feature over here.
Forum discussion at Twitter.