To my knowledge, Memorial Stadium hasn't been used for much else, until recently. A lot of professional stadiums get used for concerts and other major events, but it seems like a lot of college stadiums aren't used for the same.
Memorial Stadium had the Garth Brooks concert in 2021, before that you had Larry the Cable Guy in 2009. Last musical performance before Brooks was Farm Aid III in 1987. (https://news.unl.edu/newsrooms/today/article/garth-brooks-performing-at-memorial-stadium-aug-14/)
Memorial Stadium hosts the high school football championships, but it really isn't used for much else. Would be smart to try and utilize it for more, if you have the turf.
I'm assuming not being allowed to sell alcohol (until recently) was the big factor for not getting concerts.