An update on this issue.
Gordon supplied me with test software that showed that the hardware was working as expected. He’s produced an RC3 version of the RoonReady software, and although that was better, my RPi2 didn’t always show up in Roon.
He then suggested that I update the RPi2 firmware using Raspbian:
- using a standard raspbian release
- log in to pi
- update the pi firmware (sudo rpi-update)
- check pi boots as expected
That seems to have done the trick. My firmware dated from at least a year ago, and this may have been the issue. At any rate, using the RC3 and the newly-updated firmware, the RPi2 is now showing up as a RoonReady device.
Thanks to @mike and @Gordon_Garrity for their help in getting me this far. Now to listen to some music.