While the authors promote their own software solution for building your Zettelkasten, I am happy a user of (and not affiliated with) https://bear.app https://be

While the authors promote their own software solution for building your Zettelkasten, I am happy a user of (and not affiliated with) https://bear.app https://bear.app which I use on my iPhone and Mac for organizing my plenty notes for software engineering, meetings, management notes, my Psychology study notes and anything private as well. In analogy to Zettelkasten I put my notes into different (nestable) boxes what they call hashes. The app eco system is quite hacker friendly as they publicly document the underlying SQLite database. I don't that possibility because their apps help me organizing my notes well enough til this point.