First and foremost thank @vittger over in this thread where the method was posted - HERE
Reason I am making this Guide/post is it seems like even though its been posted, theres not a thread for it and some miss the actual method of doing it.
I haven't tested or seen it tested on any OS below Android 7.0 so it may not work unless you've updated.
2.Install the APK
3 Open the App
4. Scroll down & Select IOT(CDG2)
5.Select LTE setting,Select Operation Mode, Then Select Lab Network
6. Device will reboot, Then go back to step 3,4, and 5, and the option Band25 make sure its enabled. scroll down to LTE Data roam config, and enable all the bands towards the bottom in that menu as well.
7. Go back to the Hidden menu APK main menu, ModemProtocol, RAT Selection, then choose GSM/WCDMA/LTE Auto
8. Reboot and you should be good to go!
9. You now have you Sprint LG G5 LS992 GSM unlocked for both US and international GSM carriers
To Add your APN (for data):
Go to, The hidden menu APK, IOT(CDG2), LTE Settings,
APN settings and then add your APN for your carrier
Remember you'll need to set APN type to "default" and
authentication type to "None" or else it wont work
Tested and working with AT&T 3G/HSPA,4G/LTE And T-Mobile
Here's a quick YouTube video I made,