The data below comes from EEDAR's PlayerPulse tracker - an ongoing survey that polls 1,500 active North American gamers per month about their habits and title awareness across mobile, PC and Console platforms. (Note that all data below is based on an aggregated 12-month sample collected from January 2017 to January 2018 and encompasses the launch of the Nintendo Switch.)
As you can see, not only do Switch owners enjoying putting a lot of time into mobile titles, they also spend a lot of cash on those games. This could mean that there's some big business for mobile game devs on Switch if they adapt their titles correctly. Should be interesting to see how many mobile devs bring their content over to Switch in the next year.