Found this documentary on Disney+ this weekend... not really a true "trail", but the documentary covers two guys trying to hike the length of Grand Canyon National Park. From the looks of things, they hike the north side, sometimes at river level, and other times having to climb more than 3,000'. Pretty much the entire trip is 'off trail', and at times takes them to some truly dangerously exposed walks along, along with side canyons that requires repelling gear.
While there are a few political commentaries along the way (such as the controversial Grand Canyon Tramway/Escalade, which at the time of filming had not yet been voted down by the Navajo), there's much more "thru-hiking" like stuff in the documentary. They even compare the trip to trying to thru hike the AT or PCT (the distance they hike is only about 1/3 the length of these popular thru trails, but make up for it in the difficulties faced).