Good day fellow-Fairphone-users! 
I didn’t touch the system very intense.
But I do know the following:
- the extended internal storage is encrypted
- photorec can not access the USB-connected Fairphone as source
- photorec can not access the Fairphone using “USB-debugging” mode
- I double checked the content on the phone using ubuntu, windows file-explorer and ABD-shell - still no media file listed and no way to copy hidden files from the regarding folder-structure
Maybe someone can tell me, how to mount the FP3-device in ubunto as a dirve so I can give phtorec a try?