Something @chrisaldrich mentioned on Reddit as examples of someone selling niche Zettelkasten decks. Seem more like protocol-kasten decks to aid problem-solving in specific contexts.
Saw this ad for Storyteller Tactics on Instagram: https://www.instagram.com/p/CiybhKcA3ZV/?hl=en
They're advertising for a product from https://pipdecks.com/. They're essentially selling custom zettelkasten collections of cards for niche topics!