When using the UX SDK and an M210 with dual cameras, I see how I can switch the FPV view between the two cameras but when I take a picture, there do not seem to be any options to take pictures from the secondary camera.  Am I missing something?

I found this in the UXSDK release note, it seems the UXSDK problem and not supported.
Maybe you can try to fetch the second camera instance first via 'getcameras' method and then take photos.

That is correct, with the UX SDK 4.x version you can not switch cameras on the M210 but you can if you use the UX SDK Beta 5.0 found here: https://github.com/dji-sdk/Mobile-UXSDK-Beta-Android
With the UX SDK 5.0 just set the camera index of both the RecordVideoWidget and ShootPhotoWidget

To find out how to use both the UX SDK 4.x version along with the UX SDK 5.0 version please see this article: How to use both UX SDK 4.x and 5.0 Beta in one Android Project? https://forum.dji.com/forum.php? ... D750%26typeid%3D750