I'd defer to Tomatekh on this one, but he mentioned earlier a Bantu and a West African split. A High-African and Tribal-African, akin to the Americans, was talked about much further back, too.
But I'm not sure where civs like Kanem, Madagascar, and Kongo would go. Nor whether Mali and Songhai would be better off moved into West Africa (then they could start with a source of gold and/or salt
). So, again, I'd defer to Tomatekh's wisdom before committing to any definitions.
I've somewhat generalized my earlier proposal. It's still in core based around splitting the "Gulf of Guinea" culture group from the "Bantu" culture group (and when adding abilities, these two groups should serve as the basis to draw from), but, in terms of civs that are/will get made, a more general "West African" vs, well, I still need think of a name for the group but it’s mostly still a core Bantu group but more generalized to Central-South Africa.
With "West African" instead of "Nok" for the title, Ashanti more comfortably fits in the group (although it did fit before) and you have the option to move Mali and Songhai into the group. Gameplay reasons it works out as the Nok group should focus on areas such as Mining/Metal-Working, Religion, and/or Siege/Fortifications, and the first two of those, at least, works out really well for Mali and Songhai. (So the current Sub-Saharan mining theme should go to this group).
Kanem (not in West Africa) and Maasai (not Bantu) still serve as outliers, just next to the core regions/cultures. However, with West African already generalized, you can label Kanem in the group if you’re set on not adding them to the Islamic group, and, once it’s renamed to something more general, the Maasai fit with the Bantu civs as a Central-South African group.
West African:
Mali, Songhai, Ashanti, Benin, Nri, [Kanem]
"Bantu/Central-South Africa":
Kongo, Zimbabwe, Zulu, Imbangala, Monomotapa, [Maasai]
This nicely gives 6 civs to each group, though, I’d say least one more high-quality civ needs to be made for both of them before it justifies the work to split the African group.
Madagascar is Austronesian, it really shouldn’t be grouped with any of the African civs. If it wasn’t for some oddities I’d say group it with Champa and Indonesia, the other two Austronesian civs. Otherwise, maybe even Oceanic... idk, there's always going to be that one civ that will never fit. If nothing else, and you're dead set on an African grouping, just have to make sure the new name of the Bantu/Central-South Africa group is general enough to include them (even if none of the abilities would make sense).