Just tried bundling your project to Android and installed the resulting app and it worked.
From ADB:
...
D/defold ( 8604): DEBUG:SCRIPT: Testing protobuf's methods
D/defold ( 8604): DEBUG:SCRIPT: Hex: 0A 04 69 6C 73 65 10 12
D/defold ( 8604): DEBUG:SCRIPT: Deserialized: {
D/defold ( 8604): age = 18,
D/defold ( 8604): name = "ilse"
D/defold ( 8604): } --[[table: 0xa3fe2720]]
...
Are you using the “dev app” that is available on d.defold.com? (Or any other prebuilt Defold Android app?) It’s important to remember that native extension code is not “hot reloadable” or automatically deployed when you do “Build & Launch” with a running Android app as a target. You can however bundle your app once with the native extension and install on your Android device then use it as a target if you want to hot reload/build&launch with Lua and collection changes. Makes sense?