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?
Obsidian is my go to for D&D.
They still sprinkle a bit of their own stuff into the markdown but it's generally usable outside.