Well Glenn, I haven't run this route in its entirety, but have run it across the UP of Michigan, Wisconsin, and Minnesota. I love trips on the back roads as compared to the interstate highways. I appears that they consider US-28 across the UP as part of the route as well as US-2. There are so many great places to stop and see all across both routes in Michigan's UP. Last summer my sibs and I took a trip out to the Black Hills and took US-2 across the UP and over into MN before we jumped off to take some more direct roads to connect with I94 at Fargo.
One really neat thing we did was NOT make reservations at campgrounds, but instead since we were travelling during the week, we used city and municipal campgrounds which were much less crowded and had all the amenities. Of course, we were not laying over for days, so it worked well. The nice thing was they are always in little towns or just outside, so within walking distance to everything. Little towns have some great character if you take time to investigate them.
I've attached some links we found useful in case your interested:
This link you may already be aware of:
https://roadtripusa.com/the-great-northern/
These two were very useful in locating/contacting campgrounds:
https://freecampsites.net/
https://usparkadvisor.com/