You must be careful not to equate being of the Lost Tribes with being of one race of people. Yisrael is a nation of many colors, just like the Coat that Abba Yisrael made for Yoseph. Do not fall into S.A.Tan's trap of pitting one group of people against another because of skin color. Yisrael is "mixed" among the nations and scattered to the four winds as Yahweh says. Only Abba Yahweh knows who we are and we recognize who we are once he awakens us to the truth. In focusing upon Israel only going to the North, you miss important scripture in Isaiah about how to identify Yisrael, and where they can be found. Also, Ephraim and Manasseh were of color. The people the Americans refer to as African Americans are not Africans. They are Israelites. My family migrated from Israel by way of Greece, France and England; and, then came to America. Because my skin is brown, most people mistake me for African American; however, I have always known that I am a Yahudi by birth right. My parents are Israelites, and having shuved in accordance with Hosea 14: 1& 2 and Daniel 9 (RSTNE), I belong to the Yisrael of Yahweh.
The same nonsense that lead to the split during the days of Rehoboam, skin color, is being tried again today. You have only to look to the Land to see how Yahudah is treating the Ethiopians and others whose skin is darker than theirs. so be careful to declare full truth and not partial truth.