I agree DNA can’t determine Jewishness, but it can determine heritage or bloodline. I’m no expert in the field, and haven’t a clue where to begin, but where there is a will, a way can be found, or God will provide one, such as the technology which exist today.
It’s also possible that such identification will only be made at the resurrection.
Another teaching is that a prophet, or Elijah himself, will identify Jews and tribes. No reason tech couldn’t help.
By DNA, most people will have some descent from Abraham — he was 4000 years ago. That’s enough time for his genes to dissipate to some of the Chinese to some of the Irish and to some of the sub-saharan Africans. Perhaps even you, amorphous.