Mine didn't find any new apps either, but I added the step for posterity. But still after I toggled over to Android Auto I now saw Gaia in the app drawer. Check yours...
Ah crap - you're correct. I remembered going to full screen (no 2nd pane) but it turns out that only works with the factory nav screen on, not using AA or Carplay.
Correction - my phone is now automatically connecting to the projection network every time I start the car. So Gaia and OnX are now always appearing in the Android Auto app tray.
As many of you Android folks have figured out - Gaia and OnX are not immediately working with Bronco's Sync 4, although it does with Carplay / Apple phones. It's not difficult to get it working. I now have both OnX and Gaia projecting to my Sync screen.
How to in this separate thread...
I submitted a bug report / support request and separately a feature request to Gaia to see if there's something they can fix from their side. However, I really think this is an issue from Ford Sync's side where they're not recognizing Gaia (or OnX) as a Sync supported app.
Regardless, you can...