I found that the new Notes and Lists service is now available in the Google Assistant settings on my Pixel 2. The service not only supports Google Keep but also other apps including Any.do, which I just recently started using as my personal list manager.
It’s odd that the service is intended for Notes and Lists, indicating it was probably original conceived for integration with Keep. With it configured to work with Any.do, it doesn’t appear as though I can create and store notes. I don’t doubt that I could create notes if I set it up with Keep.