The Lemba people would be Levites by ancestry, and Levi was a son of Leah, whereas Manasseh was a grandson of Rachel. Presumably Leah and Rachel were full sisters (at least there doesn't seem to be any indication that they had different mothers) but that would only be important if they were examining the mitochondrial DNA.
Has DNA testing been done on the Falashas of Ethiopia? Not everyone believes that they are really Jewish by ancestry and that would be a possible way to resolve the question.
I didn't raise the issue of the British-Israelites and have no interest in that topic.
http://www.khazaria.com/genetics/abstracts.html
Samaritans are descended from Israelite men and Assyrian women.
Those Lembas who possess the Cohen Modal Haplotype have Middle Eastern ancestry, possibly Jewish Cohen. The Buba clan is especially Middle Eastern in its paternal DNA.
Many Spanish-speaking Latinos of the American Southwest are descended from Anusim (Spanish Jews who were forced to convert to Catholicism).
The Mizo people of northeastern India, the self-styled "B'nei Menashe", have no proven genetic connection to the Israelites.