In Data Grid 2, to make it available as a “Listen to” option, you first need to enable selection. Go to General tab → Selection → Single.
Once that’s set, the grid will appear as selectable in the Data View.
You can then choose your preferred selection method, either Checkbox or Row Click.
dJason,
From the documentation for Mendix 10, seems like it should be available:
Curious if that works for you.
Mike
###EDIT###
I tested this in 10.24.9 and selecting Selection-Single and Selection Method-Row Click enabled me to select DG2 as a listen to datasource.