I’ve put in some more work, and I’m pretty confident that most things work now (except the download / install dialog)
It should register packages on first launch, with menu items appearing asynchronously. Besides a dialog asking if you want to install the packages, launches (and re-launches) are pretty much instantaneous.
So the next step is to start connecting the New plugin index and updating the “Install Plugins” window.
I’ll also start updating a few of the example packages.