It's happened more than twice.For me, the measuring bar is being ranked in the top 25 – preferably at the end of the season. Since my time following the Gophers (30 years – starting while attending the U), this has happened twice – 18th in 2019 and 25th in 2014.
In 1999 they finished 18th in the final AP poll
In 2003 they finished 20th.
In 2019, they finished 10th.
They weren't ranked in the final AP poll in 2014 though.
Minnesota Final AP Football Rankings | College Poll Archive
collegepollarchive.com