If I add a footer to my markup and define a
grid-area and place it on the grid using
grid-template-areas you can see that it sits below the content column. There is no clearing required as this footer has a track on the grid, it can’t hop up into another track.
This example also shows the issue described in example 5, by default the background on the sidebar should stretch to full height, in a similar way to the defaults for Flexbox.