Linux

I am surprised that no one has mentioned Rnote yet.

It is my favourite newly-created program for Linux. It is a relatively new app which supports annotating files and taking handwritten notes. You can import PDFs, set the page size to infinite or a fixed size (something OneNote can't do), adjust the background to display grids or lines or dots or nothing with any spacing you like, input text with your keyboard, .... It is available on Flathub for easy installation.

The only major downside is the following: Disclaimer: The file format is still unstable. It might change and break compatibility between versions.

I was asking a similar question a few months ago, and my search turned up Joplin. It's a free, open source app that works across multiple platforms and can sync data through a cloud service, either through Joplin's own cloud storage or through a third-party cloud storage like Dropbox.

https://joplinapp.org/

You might want to explain the features of OneNote, particularly the exact ones that you want. I get the impression that most people don't know its organization structure.

My short input: it's not just note taking. It's has a tiered level of organization for the notes to categorize and quickly move about. The example I read was like it's set up like you have multiple binders, with dividers in each, and pages (notes) within those. The page is very open ended, you can add text boxes in any spot, mixed with pics in any spot.

I looked at Joplin and Obsidian for the kind of notetaking I do and settled on Obsidian. To be honest, both have more features than I use. I like Obsidian because it's based on Markdown, so you're not tied to some oddball file format. But you should try them out and see which one fits your work style.

I'm not sure what features of OneNote you are talking about, but maybe logseq will suit your needs.

I use logseq and notesnook.

Saber

Probably logseq or Obsidian, but... if you like plain text and really need customization you might go with what I use: emacs + org-roam

https://orgroam.com

Guides

text: https://jethrokuan.github.io/org-roam-guide/

video:

Start Using Org-roam Today | Install, Configure, and Use https://piped.video/watch?v=AyhPmypHDEw

Setup Trilium and use the Firefox extension to save screenshots or the whole page to it automatically which I love.

I'm feeling old. I have a folder called Notes with a directory hierarchy with text files in them. If I want to edit something, I navigate to the appropriate directory and type "vim -S". If I want to get to them remotely (which I haven't really needed) I would SSH in to my system with whatever terminal emulator I had available.

You might look at these relative newcomers to this category of app...with some caveats for why I haven't switched from Obsidian.

1. 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!

2. 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.

There's a program called cherrytree that I think is very underrated. It's probably not a 1:1 replacement for OneNote but I recommend checking it out in case it fulfills a similar but different need.

Some which I can think out of my head are : Joplin Trillium Logseq Notion Obsidian Anytype

If you need to draw, I would look into notion and obsidian.

Here's an Obsidian RPG Video: https://youtube.com/search?q=obsidian+rpg

I ended up going with obsidian. I wanted absolute portability I needed multiplatform support. I hadn't heard of Joplin at the time I made my choice, but I can say I'm happy with Obsidian and I like how their documentation is dog-fooded and useful in that form.

Joplin is very advanced

This came up a few days ago in another community, and it sounds like the poster may have actually had a similar use-case to your own.

A Text File... No, really, a simple text file is imo the best way to take notes, you can open it on any computer, it's fully FOSS, you can sync it in 100 different ways

Joplin self hosted on a NextCloud instance!

Only because self hosting is satisfying and fun. You can have your Joplin notes synced on OneDrive as well.