One of the original reasons I adopted Emacs (after evil-mode was created) was Org mode.
I use it for time tracking; agendas; note taking and organization; recording and graphing of data; preparing, rehearsing, and rendering slides for talks; cross-references to emails (Gnus integration); literate programming; my emacs config; project planning; Kanban; and much more.
Add .gpg to the file and have your notes automatically encrypted by Emacs.
Here's a couple of my past talks in Org (you can see it evolve via Git):
You can see how the document evolves, e.g. as I rehearse each slide, via Git:
I didn't include my associated time tracking in here (which I kept in a separate file that linked to it) for privacy reasons.
These source files produced the actual slides, using Beamer (LaTeX):
Mike Gerwitz's personal Mastodon instance