I'm asking this here because I figure developers know the most about the android file systems.

Is part of the file system on a Samsung S9 andriod cell phone hidden from the user? And, if so, is there a way to see all the files on the phone?

I ask because I am unable to find the files for the audiobooks on my phone I that download from my library with a laptop (running on Mint Linux) using the Cloud Library. The library page says they are *.mp3 books but I can't find any *.mp3 files anywhere...

I use the laptop to check the books out and then download them from my android phone to listen to them. I am told that the laptop streams the audio for listening to the books and the arduino downloads and stores it on the phone.

Jack
I think I found my own answer here:

https://www.androidauthority.com/phone-storage-folders-explained-744100/

And if I understand it, that is a lot of stuff you can't see unless you unlock and root a android phone.

This page is not encouraging as far as seeing much more:

https://www.androidcentral.com/root#F

It says there that ".. all the U.S. versions of the Galaxy S9 are locked up and encrypted..."

Jack