I just started using orgmode to compliment notion. So far it feels to me as Notion is a bit like emacs / orgmode without API, and orgmode is a bit like notion without collaboration.
The nice thing about org-mode is that it automatically gets all the cool stuff that emacs has. (Although, I have never tried any of the solutions listed in that wiki page and I suspect even the "working" ones have issues).
https://org-web.org
https://github.com/DanielDe/org-web