Wow—when I run adb shell dumpsys location I get a flood of information, and it isn’t clear what I should be looking for or what might need to be different from what’s currently shown.
I’ll note that, as mentioned earlier, location works fine—the Maps and Bliss Weather apps function perfectly.
However, Find My Device (FMD) does not work with either real or fake locations. In version 3.1.1 the phone sent back the secret code to the other device instead of coordinates; since updating to 3.1.4 it doesn’t even send that code anymore. Instead, the screen displays “Find my Device by SMS Tracking location in background” and a notification sound plays whenever an SMS containing the secret code arrives.