Postscript: Although I believed I had succeeded last night due to producing a complete APK, what I did not know was the APK I thus built does not *run*; installing it leads to "Failed to extract native libraries, res=-2]", a catchall error message with several possible causes but seeming to imply a bug in a official Android tool such as zipalign.
I have returned to building the Android binaries on my old Mac laptop, and those work.