Org-mode
An Emacs mode for structured text that has grown into a complete system for notes, task management, planning and literate programming. Started by Carsten Dominik in 2003.
Everything is a plain text file with headings marked by asterisks, which means the material survives every tool change and versions cleanly. On top of the outline sit TODO states with timestamps and an agenda gathering everything scheduled across all files, tables with spreadsheet formulas, per-task time tracking and export to HTML, LaTeX and PDF. Org Babel runs code blocks inside the document and inserts the results — the same idea as Jupyter, but in plain text and with several languages in one file. The org-roam package builds a zettelkasten on top. The drawback: it presupposes Emacs.