Transfer Android app with offline data to NEW PHONE without ROOT

I've purchased a new phone and have transferred most of the data from the old device to the new one using various means. There is one app, however, that does not have account login, so I cannot save cached data in the cloud. Meaning that I have no choice but to move/restore the app to the new device with the offline (cached) data. This app is quite important to me, and I need the offline data. I know of the following techniques to do this: - Backup and restore app + cached data using Helium: copy & replace the 'sdcard/carbon' folder from the old phone to the new phone. After doing this, *restore* the app with data on the new phone. - Root the device and use Titanium backup to do the same. - Backup apps using the 'Backup' feature in Google Drive. Helium just did not work (with a brand new phone with Android 8.0!). I cannot use Titanium as I cannot root my old phone at this point (before backup is complete). And **restoring** the app this way will in all likelihood require that I root my *new* phone as well, which is a deal-breaker. Does Google Drive Backup work with all third party apps? I did not see the app I want to save in the list of apps whose data was being saved by Google Drive. What should I do? Can anyone advise? **EDIT**: All of the techniques given on various sites for both partial and full backups (including nandroid backups) are *device specific*, i.e. you can restore to the *same* device only, not from one device to another. This includes both **Droid Explorer** and **Simple ADB Backup** too, apparently. Is there no general way of restoring an app with data to a new phone without root? Google Drive backup does this without root. If it can do that, why can't other apps? Also, various people suggested using **MyBackup Pro** / **Android Assistant** / **DrFone+**. All these tools give up before even trying: they *all* seem to require root.