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?
You might look at these relative newcomers to this category of app…with some caveats for why I haven't switched from Obsidian.
Acreom - Not open source yet, but planned. Flat markdown files like Obsidian and Logseq. Dealbreaker for me is that in order to use the app on Android, you have to sign in with Google, Apple, or Github and use their cloud for sync. I'm trying to convince the dev to allow their "local first" mantra to permeate all versions of the app regardless of platform. He is very receptive, so we'll see. If they do, I can see myself switching to Acreom instead of continuing with Obsidian. But that's the beauty of open file format, you can pack up and leave very easily!
Notesnook - Is FOSS. But not self-hostable yet. That is on their roadmap. Potential dealbreaker is that it doesn't support markdown, rather shortcuts that behave similar to markdown syntax. As a result of that and their E2EE, the file format is not as open as Obsidian and others that use simple .md files.