In the past I was able to use iOS devices as USB drives.
(It may have been on Windows only, and/or the devices may have had iOS < 9)
At present my iPods / iPads / iPhones do not appear in my Mac's:
The complicated guides to trick-mount iOS devices, such as this one from lifewire, that mounted devices on desktop do not work. (with iTunes 12 on macOS High Sierra)
Similarly, the devices do not appear in the /Volumes folder anymore, neither in Finder nor Terminal. (The only volume I see there is my SSD - the system drive volume)
I have set my system volume to show all files - using a Terminal command:
defaults write com.apple.finder AppleShowAllFiles YES
Is there any way to access the iOS files in macOS directly?