As a freshman in 2020, Arnold hauled in six receptions for 45 yards.[4] He caught three passes for 33 yards and two touchdown in the 2021 season opener, a 17–14 win over South Dakota 17–14.[5] Arnold finished the season with 27 receptions for 316 yards and three touchdowns.[4] In week 4 of the 2022 season, he made four receptions for 84 yards and a touchdown in a 35–27 win over Duke.[6] In week 7, Arnold brought in five receptions for 113 yards and two touchdowns in a 52–42 loss to Oklahoma.[7] In the 2022 Liberty Bowl, he made eight catches for 119 yards, but the Jayhawks lost in triple overtime versus Arkansas.[8] Arnold finished the 2022 season with 44 receptions for 716 yards and four touchdowns.[4] Ahead of the 2023 season, Arnold was named to the Earl Campbell Tyler Rose Award watchlist.[9]