Today there are over 500 federally recognized tribes, many more that are unrecognized by the government. Pre-colonization, when Indigenous diets weren’t oppressed, there were more tribes than that. Each tribe had their own diet based on where they lived (coast ate fish, plains ate buffalo) and how they lived (for example if they traveled with the seasons or stayed put).
Tribal people had fire so food could be cooked. They also had systems for drying foods into jerky and dried fruit and pastes. Some tribes also had advanced agriculture systems.
So really tribal people ate from the earth but this could mean any number of things. Some tribes were hunters and gatherers, some were agriculturists, some were other “labels”. And don’t forget the power of trade as well.
Post colonization tribal people were forced out of their homelands and so did not have access to traditional foods. Then where they were re-homed they weren’t even allowed access to the land around them anyhow. So they lived on government commodities that were grossly sub-par. Flour was most often infested with grubs for example. This is where the “traditional” Native food of ‘frybread’ came into play. It was one food that could be created with government commodities and few ingredients. It is similar to an ‘elephant ear’.