I can't recommend nand2tetris highly enough – it's a great crash course in computer architecture, operating systems, compilers, etc. but also it's just mega fun.
A big part of the joy came from making up my own extra credit side quests: implementing a compile-to-WASM emulator for the hack machine, adding optimisations to the compiler to produce smaller and/or faster programs, etc.
For getting Apple Health data into duckdb, I’ve used this in the past: https://github.com/dogsheep/healthkit-to-sqlite. (You can load the SQLite database directly in duckdb.)