What are some quick go-to resources or important facts about single-payer healthcare as a political achievement?

A friend has an up-and-coming TikTok account related to medicine, but it's currently focused on baby-related content.

He's a total lib but wants to be left on single payer. His uncle (communist btw lol) had an infamous testimony to Congress about single payer in the 50's? But he doesn't know a lot of the technical side. He's also in support of abolishing private doctors, which I think isn't something that comes up in the single-payer argument?

Is there a go-to place for a scholarly nerd for this sort of topic? We have Rosenthal's book, but it barely mentions single payer. Or are there some quick-hitting essential facts I should consider?