Unable to deploy built-in apps with Intune

I'm attempting to deploy apps from the "built-in apps" catalog provided by Intune, as this seems to be the preferred/recommended mechanism suggested by Microsoft (when available). 

Here's a specific example. Take, for example, "Microsoft To-Do", which is available as a built-in app.

If I add the app the "old way" as a "Managed Google Play app", and assign it to my test group, it applies and gets deployed/installed successfully. Now, I try using the same criteria but instead add the app from the "Built-in apps" catalog, and it never deploys, and is listed as "Not Applicable" to those in my test group. I've tried every combination possible, and have verified:

- We're using Android 9+ on the test devices

- The devices are all either enrolled/managed, or BYOD - it doesn't matter

- The devices have Work profiles

- The app isn't already installed 

Is there any place where Intune might log or provide more information as to why it rules out a device/user as "not applicable" for a given app/policy? I am stumped, and can't get any Built-in apps (so far I have tried about a dozen different ones) to deploy.

Bob