Why do I take notes? So I remind myself stuff when I invariably forget.

You can use vim to keep notes in plain text. Several plugins are available to help with this:

• https://vimwiki.org a feature-rich wiki with mediawiki syntax and markdown support
• https://ratfactor.com/repos/vviki/ stripped-down vimwiki with asciidoc

You can manage your tasks locally with something like Nullboard: https://github.com/apankrat/nullboard

toodoo app for Android is lightweight. Recently updated for modern Android versions so task exporting works.

todo.txt format is interesting, although yet to find (search for) a TUI tasks with calDAV support on linux