If your version of Android is from December 2018, then it HAS ALREADY had update(s) -- the Gemini was released half a year before that!
The latest version is Android 8 from May 2019, so you should be able to upgrade to that, either through the built-in Firmware Update, or by downloading it from Planet's support site.
Of course, it would be nice if updates were a bit more timely, but they do happen.