Yeah, the Congo Tribal lands deserve their own PDF sourcebook....maybe I'll write it, I spent a few years in the DRC in the early 90s.
The problem is, the map of
Sixth World Almanac call "Congo Tribal lands" an area that stretches from Niger and Chad to Mozambique. It doesn't appear to match anything, be it Congo as a country, the Congo river basin, the Kongo empire or the Kikongo language. The distribution area of the Niger-Congo linguistic group is much larger, but it doesn't fit: it goes all the way west to Senegal, while Niger and Chad ancient languages are in the Nilo-Saharan group.
Labeling it as the "Saharan-Congo Tribal Lands" might be more appropriate, since the area would include tribes from both the Niger-Congo and Nilo-Saharan linguistic groups, while not including the Niger and the Nile rivers proper. On the other hand,
6WA map shows a much greener Africa, where the Saharan desert somehow ends around 25°N. So the Saharan adjective may be considered misleading, and "Sahel-Congo Tribal Lands" be a better idea.
That is, unless the tribes from Congo proper managed somehow to pull out one of the largest military conquest in history during the 21st century.