Let's avoid borderline idolatry concerning certain historical figures; it only leads to unreliable narrators who embellish the achievements of those from their own tribe.
The SSDF was the first rebel group, and it's important to recognize that tribalism didn't begin with the civil war or Barre's rule—it was exacerbated by them. Its roots can be traced back to the grievances of MJs in the government after the assassination of Sharmaake and the concentration of power in Barre and his circle.
It was the initial force to openly challenge the government, attempting a coup, capturing several towns in the early 1980s, which led to reprisal killings by Barre. As the SNM gained momentum, Barre attempted to consolidate Daroods under his control, under "Daroodnimo." It mostly worked as he quelled and gained support for a while for his war in the north from the SSDF and its power base..
As the situation deteriorated, the SSDF regained strength when Barre's power waned. While some exiled leftist members joined the SSDF initially, they soon left due to their lack of tribal support. The original SSF members held most of the power within the SSDF. They solidified control over their tribal territories, forming PL.
None of these groups directly served Ethiopian interests; their common goal was to overthrow Barre. Ethiopian support for the SSDF flipflopped, as Ethiopia itself faced internal unrest during that period.