Ask HN: Which Substacks consistently unlock insights for you?

I'm looking for Substacks that somewhat consistently provide genuine "aha" moments or deep perspectives. Particularly interested in:

- Programming and engineering (especially functional approaches but open to anything) - Economic and financial analysis beyond surface-level takes, but still layperson-friendly - Systems thinking/mental models, critical thinking

Honestly I'm open to anything interesting or thought-provoking, even if it's totally outside these domains. I’ve enjoyed writing on history, design, and art when written by someone who knows about the subject and about how to write about it. Completely new to Substack and finding my feed a bit lacking.

(Also do plug your own if you write! HN comments are a huge source of “aha” moments after all :)