Not FOSS, but I'm a big One Note user for work and wanted to find something for my personal life and most likely will use it for my next professional role in at least some capacity...Notion is by far the most customizable and complete solution that's also user friendly because of existing user templates. I've been SERIOUSLY impressed and I've been trying everything I can find.
Best part is that the phone and computer apps are both very capable. One Note on phone is the worst companion app.