Switching between launchers is a common thing on Android devices, and since LG G5 doesn't have an app tray, you may want to change default launcher on LG G5 and try 3rd party launchers on your modular phone. Well, to change the default launcher on LG G5 and switch to another launcher, do as follows:
1. Make sure you have already installed a launcher from Google Play Store or the LG World app
2. Open the Settings app and set it to the Tab view
3. Go to the Display tab
4. Touch the Home Screen option, under the Home & Lock settings
5. Now, under the General settings, tap the Select Home option to see the list of already installed launchers on your LG G5
6. Select your new default launcher, by touch its icon and hitting the OK button. Don't forget to mark the Use as Default App option.