ND has played the Shamrock series three times in Texas, in Arlington and twice in San Antonio (most recently in 2016). They played Pac-12 teams (Washington State and Arizona State) and Army there. Most of the other games have been against teams that were regularly scheduled, but whose home stadiums maybe weren't as exciting as playing in another nearby venue--with the exception of Miami at Soldier Field (others were Army and Syracuse at Yankee Stadium, Boston College at Fenway Park, Maryland at FedEx Field, and Purdue at Lucas Oil). Although not part of the Shamrock Series, they have also played Navy in Ireland (and will again in 2020), and when they play Navy away, they play all over the place, including San Diego, Jacksonville, FedEx Field in Maryland, and the Meadowlands.
I don't understand the whole thing, but ND seems to like playing in those venues.