Sorry, the furthest north public land with dispersed camping is Morgan Monroe Forestry.
Your best options for real secluded camping in N Indiana is a private land owner or catching a lucky spot at a for profit campground with no neighbors.
Dispersed camping on public lands map: https://gisdata.in.gov/portal/apps/webappviewer/index.html?id=fa241937d1e84c9cbb91aba208c578d5