I’ve used it a lot in packaged games, so I know it works. Are you sure you’re opening the correct port number on the packaged version? Or that the game or the Arduino IDE is not still using the port when you try it? Do you close the port when closing the game?
2.2.1 is the latest. I removed the engine hotfix version because C++ APIs don’t change between major versions, so the hotfix version doesn’t matter.
Just add " .1" at the end of the version string. (4.16.1)