in asimov's foundation series (for which this is mild premise spoilers), some intellectual elite of a civilization put together The Foundation, a planet-organization tasked with preserving mankind's knowledge during an expected incoming dark age. it might be worth considering doing something similar in our own timeline: write a large book, with instructions to learn to read it as well as providing the bases of rationality, and warning its readers to be wary of AI risk and other existential risks in their civilization. we'll have failed, and we want them to have a better shot.
it needs to largely encourage its propagation, but also some ability for future people to improve upon it. it needs to allow its users to quickly outcompete others. it needs to be physically printed in many copies, to be distributed across the world — including poor countries — to maximize our chances. as the foundation for something more like dath ilan and less like here.
a whole organization would be even better, if it can survive — but i feel like a repository of ideas is a more robust format, and communities can form around it and implement it.