I may have found part of the problem with adb logcat.
I assumed it was analyzing the [app].apk file, but on further reading it is the phone device which produces the log, so it needs to access that device. I have the development computer isolated from all connections in order to protect it, and everything (ndk, sdk, jdk etc) is set up on this, with the [app].apk file transferred via sdcard.
I'll either have to set everything up again on the connected computer, or find another way to identify why I get the
"Unfortunately, [app] has stopped." message.