Empire of Shadows by George Black touches on this. https://www.amazon.com/Empire-Shadows-Epic-Story-Yellowstone/dp/1250023203

In short, the rumors that American Indians were "afraid" of YNP is a myth. There were no year-round habitants, but that's because Yellowstone is freezing. And, remember, Yellowstone is massive. Certain areas were often inhabited by the very dangerous Blackfeet, and they'd stay away. Other areas were less hospitable, and so weaker bands of tribes (like the Sheepeater Shoshone) were forced into them.

Here's another good read. https://www.usgs.gov/observatories/yvo/news/land-burning-ground-history-and-traditions-indigenous-people-yellowstone

Fun topic!