It's been quite awhile since I lived in Indiana (20yrs) but back then about all I remember was either private offroad parks (Badlands or Haspin Acres) or there is a bit down in Hoosier National Forest.
Found this info in the Indiana check-in section of the site.
Crossoverlander provided some maps that you can use with some routes in Indiana. He has a link to some Google maps at My Maps that you can use to extract the gpx trails that you are interested in. We did the Shades/Covered Bridges trail. Some pavement, lots of gravel roads and some dirt. Pretty easy, but scenic.
There are a few places. Badlands offroad park, haspin acres, red bird state rec park, then there are a few gravel roads with some nice river crossings I know of in southern Indiana. If anyone is interested in getting out today or tomorrow to explore any of these options, I'm game.
I dont know of any trails in Indiana, but ya might try Land Between the Lakes. Its not that far away, and it is absolutely fantastic! Gaia is pretty accurate out there, and Avensa Maps works good at Turkey Bay offroad area.