Trying to find out what app is being used with the “sharing” notification as pictured Sharing notification-top left of phone
Which is that app?
Open the notification tray and the application's name should be written there for each notification. (Android 7.0 Nougat and above)



Here are two examples:

As you can see, the app name "Termux" is visible next to the application's notification icon.



Here's another example, where you can see the app name "Hangouts" is written next the application's notification icon.



None of this has anything to do with rooting your device, it's built in to stock Android.