Unable to Access the Internet over Thread from Android Things

[MSohm]

I'm trying to connect to the Internet from Android Things connected to an NCP through the OpenThread Border Router.

1 Raspberry PI running Open Thread Border Router. This device is also connected to IPv4 ethernet connection to the Internet.
2 Raspberry PIs running Android Things
Each device is connected to a Nordic nRF52840-PDK over USB.

The border router is configured as described here: https://openthread.io/guides/border-router/build
I have tested with and without performing the "Wi-Fi Access Point Setup" steps, performing or not performing them makes no difference.

I am able to run non Android Things examples and connect to the Internet through the Thread network, so Internet connectivity through Thread is working.

Using the Android Things LowPan sample and Thread network created by the Border Router, two Android Things devices are able to see and connect to one another.

I then modified the LowPan sample to connect to servers outside the Thread network (making a socket connection to a public web server), but am not able to connect to anything.

If I try to connect to a public external IPv4 address (converted to IPv6 with the 64:ff9b:: prefix) I get:

android.system.ErrnoException: connect failed: ENETUNREACH (Network is unreachable)

If I try to connect to a public host name I get:

android.system.GaiException: android_getaddrinfo failed: EAI_NODATA (No address associated with hostname).

What is required to have Android Things connect to a server over the Internet through a Thread network?