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.
There are good charities working around the corner but you never know what actually happens in Africa. There are many fake charities ran by scammers where money never makes it past the United States. The blockchain based project should be able to replace these with a generic decentralized charity that doesn't involve any middle parties. Only the donator and the food distributor.
Indeed there is a ton of charities working around in the community, one of the organizations that definitely have my trust is the water project organization (
https://thewaterproject.org/). They give you a report for every donation that community makes (
https://thewaterproject.org/give-water#). So, I bet the organization really solve the problems in Africa.
Like what Lao Tzu once said, "Give a man a fish, it will feed him only for a day. Teach a man to fish, and feed him for lifetime". Why not create a blockchain project that focuses on teaching or educating Africans to earn for themselves(for example an online schoool using blockchain as it's backend)? That way, you and your partners wouldn't only be helping them to get by for the day but for lifetime. It might be hard but I am sure someone out there can pull this off.
They hardly get a reliable internet connection in Africa.