I use Evernote. I have multiple notebook stacks for different topics (like each company I work on, ideas, general life notes, learning, research, etc.) and within each stack have a notebook dedicated to notes addressing topics as well (for example in the company stack have a notebook for sales notes, in the learning stack have a notebook for JS).

Evernote has worked well so far and me trying to switch to OneNote didn't work out as well. I'm still open to alternatives, but Evernote has kept my mind organised without a doubt.