You might have seen the film the Postman but have you read the book it was based on? I read it in hardcover 30 years ago and recently dipped back into it and while there are some differences from the film the stories aren’t too far removed in spirit, the strangeness is turned down a few notches in the film for the economy of story telling that is often forced on a film based on a novel.
It’s got a lot of great post-apocalyptic undercurrents going for it. We’ve got a community controlled by a computer (not in the film), rampant pollution and mutation (not in the film), rebuilding of civilization around symbols and ideals. It’s a tale of hope.
There’s great insight into the film from the author of the novel here:
I think the a campaign set in the world (worlds) of the postman could make for a decent post apocalyptic RPG campaign and such a setting with a hint of hope can be rewarding. Ragtag survivors and communities struggling to get by in a world gone mad coming together in the name of hope despite the brutal needs of survival and the ambitions of the ruthless .Give it a good read.