I appreciate all of your excellent answers and suggestions so much! And I never knew that a rapid boiling action would emulsify the fat into the broth - I never made that very simple connection!
When I posted this question, I hadn’t finished the broth. My goal was broth for French onion soup, so the color of the broth dismayed me. I was very pleased with the end result though. The broth isn’t really suitable for traditional French onion soup, but it’s creamy and rich, a perfect base for some Asian soups. And since I’m not serving any paying guests, I could make French onion soup with it. In fact, I’m gonna try it later today! It just won’t be that beautifully clear, delicately flavored broth that’s associated with it. Maybe I should give it a new moniker - Asian onion soup (the traditional cheese might pose a problem, though!)