“People I know who are definitely part Indian, maybe 1/8th but had a living ancestor who was Indian, are coming up with bupkis when they get their DNA done.”
Could be the scientists do not have a good Indian DNA sample to work with?
There is another reason. They are not related genetically, but I am not suggesting adoption.
They look Indian in the face, don’t need to shave, have very dark skin, and have a grandparent or greatparent who is verified Indian. But their DNA comes out without showing any Indian DNA, or sometimes trace amounts. It’s clear that something is messed up with the standard DNA tests and American Indian heritage. With Britain or West European or Iberian Peninsula, it all seems to check out in line with known heritage. But with Indians, it is off.