I cannot get Linux Mint to recognize the phone so that I am able to transfer files. I have done this with normal phones before including the Samsung s9.
I always found a simple FTP connection usable for the most purposes and you do not need a cable. The device is the server, the PC is the client. There are several good (S)FTP server apps.
On Linux you will also find a software called android-file-transfer. This needs a cable but you can access both the SD card and the device memory as well.