To solve WHICH African problem? I think it's hard to come up with ideas or assist you in any way unless we know what you have till now and how much strength you hold to implement the project practically.
Don't expect Africans to download a core wallet or access the product on a chain. Your solution should be like a decentralized charity that feeds malnourished African kids. Anyone sending money to the charity address must have the confidence that money will be used to serve the purpose it's intended for.
Decentralized charity would be the only way which would really help out it might not completely solve out but somehow it would really be a big help. Ive been looking for those organizations or groups that do have the same motive or project but i cant really easily entrust funds and for op he didnt mention about the exact idea on his mind on what problem hes referring to.