Abraham Bin Dawud was a Jewish traveller and historian and the equivalent of the Muslim Ibn Khaldoon. He wrote a book Sefer Ha Kabbalah in around 1161 (Around 900 years ago) some interesting things about the locations of the Children of Israel.
”You will find communities of Israel spread afar from the town of Sala (Western Morroco) at the extremity of the Maghrib( the rest of Morocco, Algeria, Tunisia, and Libya), as far as Tahart (a place in Algeria) at the beginning of it, the extremity of all of Libya, Egypt, the country of the Sabaeans, Arabia, Babylonia, Elam, Persia, Dedan, the country of the Girgashites which is called Jurjan, Tabaristan, as far as Daylam and the river Itil where live the Khazar peoples who converted. Their king Joseph sent a letter to R. Hasdai, the Prince bar Isaac BIn Shaprut and informed him that he and all his people followed the Rabbanite faith. We have seen some of their descendants in Teledo, pupils of the scholars, and they told us that the a small party of them followed the Rabbanite faith.”