@niki when you’re re-compiling your modded GO4 app you need to rename the application to “dji.pilot.pad”
There might be an old script in the repo on GitHub that does this for you, can’t remember, not looked at it for many years now.
And I don’t mean rename the APK file it outputs, there’s a manifest file or two that you need to edit 
You can then side load your new apk app on to the rooted CrystalSky and it’ll run quite happily alongside the built in GO4 app (so you’re not replacing or updating that one).
I found that the DJI OS will often try to hide the Pilot app (ie. Your custom GO4 app which is now called DJI Pilot) from view but as you are rooted already you can just unhide it again via terminal:
su -c "pm enable dji.pilot.pad"