@cosine the stock answer is "ubuntu" but on top of the way ubuntu disrespects and sells out its users and the community (amazon thing, ads in motd, not playing nice with upstream, Mir, etc.) it doesn't actually solve the problems that have long plagued attempts to "make Linux 'friendly'".
I think a software setup for folks w/o computer knowledge should focus on mitigating the impact of mistakes and on facilitating letting technical friends help them with problems