My go to way of taking notes is sending messages to myself. Previously with Signal’s “Note to self” and now with my own channel with Element. It is fast way of taking notes, but horrible in long run since you cannot group notes or add tags or anything else that you would expect from good note taking tool. I have Nextcloud notes, but I still do it since I am used to it and it is fast way of syncing notes with mobile and PC. Anyone else has interesting ways of keeping notes?
For quick notes I use unsaved Notepad++ whenever on Windows, and random text files on desktop on Linux made with KWrite.
For more organized notes I use self-hosted MediaWiki instance.