I did the same after getting the phone to connect with my linux machine by activating file transfer in the USB settings.
I first did a “normal” copy to my PC, but since I don’t really trust it I researched for an option using rsync, which works well, after you finally found out the proper settings.
I have installed now go-mtpfs, which luckily exists already compile for Ubuntu 18.04 , mounted the phone after creating the mount folder and giving it 777 access rights and now I watch the lines of a lovely rsync rushing by in my bash window.
Now I even consider writing a tiny backup script for regular backups via rsync.
$ mkdir /media/myuser/FP3
$ sudo chmod 777 /media/myuser/FP3
$ go-mtpfs /media/myuser/FP3
Then I opened a second shell and rsync to my local back up directory, which I had created before:
$ rsync -va /media/myuser/FP3/ /home/myuser/FP3backup/
The only thing, which was not transferred was a file disk/.android_secure/com.mobisystems.office-2.asec but it doesn’t look important.
Thank you for your help!