Google blender library override. Do you find anything newer than summer 2020?
Well, at least, there is blender.org.
You can find dedicated chapter in release logs of present and future releases.
You can find dedicated task on d.b.o
But imo, the reason why you can not find tutorials about them is : it is too soon.
It is for serious animation production, not just camera animation or a cool jingle video clip.
Public for that use of Blender is rarer than for rendering or sculpting.
That requires that audience is already familiar with asset creation and linking.
Asset Browser has not been officially released, yet.
Plus the fact that links that I posted are exposing that workflow is not frozen for one decade.
It is in development and will evolved. There are several milestones that should be reached before it appears to be polished.