To augment what was written above:

https://www.marriott.com/flgwb - Trailborn Grand Canyon - Williams, Arizona
https://www.marriott.com/avlhb - Trailborn Highlands - Highlands, North Carolina
https://www.marriott.com/ilmwb - Trailborn Surf and Sound - Wrightsville Beach, North Carolina

Trailborn only has four properties in total, with two additional planned in Mendocino, California and Jackson Hole, Wyoming.

The existing property that has not yet joined is Trailborn Rocky Mountains in Estes Park, CO - https://www.trailborn.com/rocky-mountains/. I can only guess that this property is a bit difficult to integrate into Marriott, because it consists of two related but separate hotels.

As of today, the integrated hotels still map to Tribute.