Hi craigguerrieri!
To answer your questions:
Forgot to mention, I have the "Home - Control 150" self-installed package. There is no touchpad involved, home portal access is via a web browser or mobile app only.
For Control accounts that use hubs (& not touchscreen), using the previous portal is how to add those devices.
I think the bottom line question here is, what URL do I go to in order to add new devices?
You can log into https://www.xfinityhomesecurity.com/sp/homepage.html to access the older portal so you can access this setup functionality. The older portal can also be accessed from the new portal using the link below the main status panel on the page.
Please let me know if this helps you resolve the issue.