For those who want a more straightforward dungeon crawler, or a spy thriller: A bunker full of old world billionaires and their acolytes wake up from cryo sleep to discover that not only did the world survive the global climate wars without them, but society no longer has a place for them at all. Seeking to regain control and to carve out a place for themselves at the top, they fire up automated divide-and-conquer tools designed to assess the weaknesses and divisions in a society and to exploit them to sway public opinion. Over time, they escalate to cyber attacks, and real world murder.
A survivalist cache is discovered by a deconstruction crew. It's recent and casts several dissapearances from the last few years in a new and worrying light. The players (possibly members of the Civil Defense?) are called in to find the survivalists and mediate things before the local villagers pick up violence again and take it into their own hands. (I'd pictured this being set earlier in the timeline, but it could be a part of the world where things are still a bit tougher)
There are investigations which can involve environmental crimes like identifying polluters - who left these barrels of chemical waste in the woods or in an abandoned warehouse? Who poisoned this river?
The players could be tasked with escorting something weird like radioactive waste on its way to a modern reactor that can use it as fuel and make it less dangerous
Something mysterious found in the municipal reuse system
I've also read about a game where the young players decided to skip the main quest and focus on the farm the DM gave them at the beginning of the story, causing a bunch of improvised rules and storytelling around growing crops, expanding their land holdings, trading with people in town etc. Not every game needs a threat to be fun with the right group of players. Sometimes the challenge of occupying a very different world is challenge enough.