GNU Emacs, which has been in active development for over 40 years, has a thriving note taking ecosystem based on Org-mode, a plaintext system for notes, documents, computational notebooks, literate programming, maintaining to-do lists, planning projects, and lots more. Ask your doctor if GNU Emacs is right for you.

Side effects may include: excessive online evangelism, endless configuration tinkering, pain and numbness in the pinkies, and smugness.