Not FOSS but I see so many YouTubers that DM talk about Obsidian for notes. I use it and love it myself, just not for DnD stuff.

Logseq and Joplin are FOSS and are often brought up. Joplins android app is garbage, if that matters to you.

Acreom isn't FOSS yet, but it's on the roadmap and I liked that one.

Notesnook is FOSS but has some features behind a paywall that might be deal breakers for some folks.

Good luck, people are just going to recommend bare bones note apps that use markdown or something and don't allow placing things where you want them.

I've looked and looked and nothing comes close to Onenote.

Obsidian is my favourite. It's not FOSS, but it is totally plaintext-based, which is close to just as good.

+1 for logseq and its whiteboard. It's the reason I switched. +It's blocks(notes/paragraphs) can be reordeded. You can pay for sync between your phone and PC. But you can use sync thing which is free and once you set it up it's pretty much set and forget. I tried obsidian and anytype, but logseq just clicked for me.

+You can write with a stylus on the whiteboard if that's your thing.

Maybe check out xournal++, has the type anywhere functionality

I'm still using Obsidian (free but not FOSS) mainly because of the wealth of plugins. QOwnNotes was another good option I used before. I really liked Logseq, but the deal-breaker for me was its approach to primarily being an outliner - and that modified all the paragraphs of my markdown notes as they become referenced blocks (otherwise it is great). I like to stick to standard markdown for portability to any future app.

If you're used to the OneNote desktop, try OneNote web.

I maintain my RPG groups' notebooks and have stuck with OneNote throughout - especially because it's easy to share access through the web application.

I really really liked this guy's video on note taking apps

https://youtu.be/XRpHIa-2XCE?si=eUMH1T7eezu_6v-V

It slowly spirals completely off the rails, in a great way

Maybe note taking isn't the best direction. Moving stuff around is more design... Maybe something like draw.io charts? Or even one of the slide apps?

Notesnook

Go for the pain tier (even though it's FOSS) 100% worth it.

You can still use OneNote online or mobile.

I wasn't able to find anything even close so I just keep using One Note https://onenote.com/

Works without any issues in Firefox.

I use nextcloud notes. They are .md and work wonderfully imo. You can either edit them through nc or through the editor on linux (or vs code on windows). Tried obsidian, never got into it and its not open source.

As someone who is writing with a pen I use "write". I think you can also type on a keyboard but moving things around as you want is definitely possible.

I used to use BasKet (a KDE program) for this, don't know if it is still alive.

I already answered, but I'm curious if anyone else can speak to using Tiddlywiki for purposes of DnD notes. It's always intrigued me as an app, but my brain doesn't seem to want to get along with it apparently.

Apart from Logseq's whiteboard feature, do consider checking out logseq's actual workflow (adding stuff in journal etc.). It does have a learning curve, but you might end up liking it more than Onenote's.

There are some good alternatives in this video: https://www.youtube.com/watch?v=P8accXNcwjs

You can also just run Onenote in a virtual machine.