So if anyone is interested, I just announced the categories for the 2026 Polymath Training Challenge :)
It's a nonfiction reading challenge that has been running for 11 years. This year, long-time participants have submitted topics, and the final list was decided by random draw.
And for the first time, in 2026 you can find and join the challenge on StoryGraph too:
https://app.thestorygraph.com/reading_challenges/a6c842ef-80fe-429b-9e66-77e0f5ea7a00