I've no problem with using LibreOffice for most of my document needs, but i haven't found a good substitute for microsoft's OneNote yet. I mainly use it to plan my RPG games and it helps a lot. What alternatives are there for organizing notes on linux, with similar features to those that OneNote provides?
For text-based notes I use Obsidian.
It isn't open source, but it writes standard markdown files to disk, so I can switch programs whenever I like and I am not locked into the Obsidian ecosystem with my notes. That was the main reason why I decided against using Joplin, especially after my experience with converting recipes from Nextcloud Cookbook to markdown ...
In general I am always trying to find a simple file-based solution for whatever I need to do. I want to be able to sync it with Syncthing instead of something fancier that requires a centralised web server or even relies on a cloud service.
Did you know that you can even sync your note using git and thus a git remote server for syncing? It even works with iOS 😃