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.
The source files don't do justice; it's best viewed in Org mode. I also use column view (C-c C-x C-c) for better viewing and quicker toggling of properties for the slides.
Mike Gerwitz's personal Mastodon instance