Install first from Playstore, copy the ... \\ Android \ obb \ com.parrot.freeflight6 com folder to a safe directory, uninstall then the app. Install modded apk, then copy back the saved folder to the ... \\ Android \ obb \ com.parrot.freeflight6. Doesn't need synchronization anymore.
I installed 6.7.3 following these directions and had no problem. I for some reason am unsure what version I needed to install the Standard or SE. I installed the one named FCC SE Battery. Can anyone confirm if this is the right one for me, I live in the US.
I will make a test flight tomorrow and report back on any issues.
I installed it on a Google Pixel 2.