This is a common issue on some android devices esp Gionee.
How to fix Unable to Set a Default Launcher Issue
- Ensure your device is already rooted
- Download Link2SD from playstore or @ https://play.google.com/store/apps/detai...k2SD&hl=en
- Launch link2sd and grant root access
- Scroll down and locate every other launcher that isn't the one you want to set as default
- Press and Hold on the launcher name then press "Freeze"
- Now, press the home button and select your chosen launcher as default
- Your default launcher issue should be fixed now. You can also convert the new default launcher to system app using link2sd to avoid the no launcher issue if you mistakenly do a factory reset.