The 6-5, 210-pounder skated in 62 career collegiate games over two seasons (2018-19 and 2019-20) with the University of Wisconsin, registering 12 goals and 28 assists for 40 points. Over the last two seasons, Miller's 12 goals and 40 points were each tied for the second-most among NCAA defensemen who were in their U20 season or younger over the span. He was named to the Big Ten All-Rookie Team, was named an Honorable Mention for the Big Ten All-Star Team, and was named a finalist for the Big Ten Freshman of the Year during the 2018-19 season. Miller recorded 22 points (five goals, 17 assists) in 26 games as a freshman last season, and he led NCAA freshmen defensemen in assists per game (0.65) and points per game (0.85) in 2018-19.