There is a closed thread here called Soft to backup apps+appsdata without root? I don’t get the reason why closing threads automatically after 6 month, anyway this is why I join this topic here. I tried helium backup: I had to grant access for the helium app with the helium desktop client (for Linux in my case). Because of a missing library, I had to install libncurses5:i386 (32 bit package). Then it started, helium got it’s access, but crashed when trying to run the backup. I had an USB-key connected to the phone, via USB-OTG, that was the reason. After I removed it, I was able to make a backup to the internal storage. Then I discovered, that there is a option in the helium app called “PC-download”. This is more what I wanted… I was able to download the backup.zip from the phone, but the restore on the second phone with the “PC download” option didn’t work.
Maybe I’ll give it another try another time…