And if there is a migration tool from onenote to the alternative that would be even better.

  • I use Joplin. Have for several years. I sync it through my Nexcloud instance. Joplin is probably what you want. I looked at a lot of stuff.

    The other software I love is the Zim desktop wiki. I have that on my main system for many thousands of notes. It has a hierarchical structure which means it scales better. It also can handle multiple notebooks too like Joplin. I find with Zim I need to split into notebooks just for speed when the collection is too far above 5000 notes.