When trying to connect a Samsung Galaxy phone to a PC, I came across this issue – the phone wouldn’t show up in the filesystem.
The first thing to troubleshoot is the physical connection itself. Sometimes the solution is as simple as properly plugging in the USB cable into the phone’s port as well as the PC’s port.
If the cable or one of the ports is not physically damaged, your phone should show up if you list your connected USB devices:
lsusb
Next, you need to make sure that when connected, the phone allows you to transfer files. To check this, simply tap on the USB connection notification on the phone. The USB Settings menu will show up – select Transferring files.
If the phone is still not mounted into the filesystem, you might be missing a piece of software.
For Windows systems, try downloading and installing the Samsung Android USB Driver.
For Linux systems, open up your Software Manager and search for gvfs. Make sure to install all available gvfs packages. Usually these are: gvfs, gvfs-backends, gvfs-daemons, gvfs-fuse, gvfs-libs, possibly gvfs-common.
You can check the status of GVfs (Gnome Virtual filesystem) on your system:
systemctl status --user gvfs-daemon.service
Another option for Linux is to go for a standalone MTP (Media Transfer Protocol) software package, such as gMTP.