The Lubavitcher Rebbe, like most Chassidic Rebbes, himself refused the title of a posek ie he refused to issue definitive Halachic rulings. He left that to the Dayanim of the Chabad Beis Din, who followed his cue.
The wave of Falasha aliya in 1985 was all set to be OK, with quick mikva immersion and hatofas dam at Ben Gurion airport.
But anti-Torah subversive leftist agitators stirred up the Ethiopians to near riot, claiming that they were already full Jews and that it was an "insult" for them to immerse and be pricked for blood.
The cowardly R.Ovadiya Yosef was bribed to back down, and thus most "sofek yehudi" Falashas were never properly megayer, leaving a doubt on their Jewishness to this day, amongst most Haredim at least.
Ironically, the latest wave of completely gentile Falash Mura end up being completely Jewish, as they do undergo full conversion!
There are c150,000 Ethiopian blacks in Israel, together with another c100,000 negroidal Black Hebrews, Bedouins, Sudanese, Eritreans, Nigerians etc.
Most make useful guards, factory workers, agricultural workers, foot soldiers etc.
Some even study Torah and become tzaddikim. Some become reshoyim: some of the worst soldiers and Yassamniks during the 2005 Gaza Deportation were Blacks.
If the total number of Hamitics exceeds 300,000, then Israel will start to become "schvartzefied", with all that that entails!