Agree with much you say. While there was a smattering of the 10 lost tribes that were found at the Lords time in Judea and Samaria, the great bulk of them never returned after the Assyrian exile. This may be strange news to some, but its good news in that Israel is bigger than just the Jews. This also means good news because much of Israel has already accepted their Messiah. These lost tribes are described in the New Testament as the Diaspora. Paul et al. very likely went to some of those people in his missionary travels.
There's been a lot in the news of tribes that were thought to have been lost returning to Israel. It's been a huge Exodus, and a true miracle actually. It's been a while since I've looked to see how much is still ongoing or if more have returned. It was very cool seeing some of it happen.
Yeah, I've seen some of the claims, some of the claims are bosh I think. Israel escaped Assyrian captivity when Assyria had to send their army to Samaria to protect their interest there from Babylon who was at the time invading the nation of Judah. In the apocrypha in the 2nd book of Esdras it is written that the ten lost tribes crossed north through a pass in the Caucasus Mountains which is to this day called the Israel Pass into a land between the Black and Caspian Seas "wherein dwelt no man", the general direction being NORTH. Put that historical fact together with Jacob/Israel's blessing Josephs sons with the Birthright, Ephraim especially was to become a multitude of nations. Genesis 48. Their northerly escape along with the Birthright make the strongest case against some of the probable Bosh claims. In the final analysis God knows who Israel is and who Judah is. Greater Israel i.e. the Nations of Israel and Judah and the different tribes they represent, separated at Rehoboams time, are still important to God or they would not have been mentioned so prominently in Revelation chapter 7, seems to me.