Backpacking opportunities in SE Ohio

Zaleski State Forest.

It’s not exactly the mileage you’re looking for, but zaleski is close. You can do 8 out, camp, and then turn around and do 8 back, or take other paths out that are more or less.

Lake Vesuvius, Wayne National Forest

+1 for Zaleski

Look into wildcat hollow in Wayne NF. At 17.2 miles it’s a little shorter than you wanted but it’s a good loop. Plenty of already established backcountry sites, or dispersed camping.

Archer's Fork is a little shorter than what you wanted at 12 miles but it has a few out and back trails that branch off that you can use to make it longer.

I personally was a huge fan of the twin valley trail by Germantown. There was a lot of variety. Pros: -lots of variety - town half way through for resupply -pretty scenic Cons: - probably 3 or 4 miles of road walking - minimal water sources I would trust (Germantown is halfway through though so you can get water there)