You might be interested in this story about a recent graduate from my university developing "Wazi", a technology-based platform that “connects remote communities to free online education using cheap, portable technology”; see:
I will suggest you use the funds of knowledge theory from Prof Marta Civil to identify what resources are available to the marginalised society, first. Are the marginalised readily prepared for edtech tools? If yes, consider Prof Keiths suggestion and many more. Ultimately, design a new tech tool which is so much connected to their funds of knowledge.