Man, I've been itching to get to a Tenere get together for years to meet up with some of the characters from this forum but it hasn't worked out for some reason or other.
The Black Hills SD area is an awesome location for a Tenere Rally offering many types of riding both street, gravel, and dirt. I'm from ND and have attended one day of a Sturgis rally, two FJR rallies based out of Spearfish SD and several Dual Sport rallies based out of several camp grounds in the Black Hills area.
We've used the Nemo Guest Ranch for a couple of our fall Dual Sport Rallies and its worked fine. There is several guest cabins for rent and lots of room for tent camping. Nemo is just South of Sturgis on a very popular Nemo highway so prices and availability may be expensive and hard to come by if your within a week before or after the Aug. 6th - 15th Sturgis Rally. The only down fall I can think of at Nemo is its a little bit of a drive to Sturgis or Rapid City if you want to eat elsewhere or pickup provisions.
I know there is already a ton of ideas out there but I'll throw out a couple others of locations we've used for a Dakota Dual Sport Riders rallies. Two other possibilities are Wild Bills Campground or the Fish N Fry Campground around 5 miles South of Deadwood. They both have small two bed cabins, tent sites, or RV hook ups, on site restaurant and bar . For 2021 we have our two Dual Sport Rallies scheduled for Custer Crossing Campground June 17 - 20 of June which has Tent sites, two bed cabins, RV hook ups and a on site Restaurant. Our Fall rally is scheduled just North of Custer SD at the Crazy Horse Campground which has a good size tent camping area and several two bed cabins next to the tent area. The Crazy Horse Campground has been used for the last two fall Rallys and is a favorite location for the Dakota Dual Sport Riders.
I have a couple of friends from the Dakota dual sport riders that also have Super Teneres and 4 or 5 that just purchased T7 Teneres. I've reached out to them on the dakotadualsportriders.com forum to get their input or see if they would like to join in for some local expertise.