I trust this Catalist data a lot more than the exit poll because its based on the actual voter file. It shows that Hillary won 18-24 year olds by 8 points (it does agree with the exit poll that the age group is a lot more Republican in Minnesota than 25-39 year olds).
https://docs.google.com/spreadsheets/d/1ILunS4s_MvMNCOyTgD3XGz88p77aQuvcGNe2BOpvnfE/An amazing stat is that 18-29s voted 23% third-party in MN in 2016.
Also, its hard to tease everything apart, but it really looks like nearly everyone in that age group who voted third party for president in 2016 and didn't stay home in 2018 probably voted for Democrats for senate and governor.
