Presently I carry a Samsung Galaxy s9+.
Your music applications will expect your music under the Music folder which is off the phone's root directory. I drag my (Linux or Windows) Music folder's contents (not the folder itself) from my computer host to my phone dropping them into Music.
The best music application for Samsung Galaxy s9 is from Samsung and doesn't come installed. To install it, look in the applications pile for Samsung, open to see its applications, then open Galaxy Apps, choose the Exclusives tab, then Search for music and download it. It will show up in your phone's application pile, probably as the last one on the last page, and be called Samsung Music.
5 Must-have Apps for Samsung Galaxy S9/S9_(free and without ads)
I installed something called jmtpfs on the way to getting this to work, but I don't think I needed to.
[email protected] ~ $ sudo apt-get install jmtpfs Reading package lists... Done Building dependency tree Reading state information... Done The following NEW packages will be installed: jmtpfs 0 upgraded, 1 newly installed, 0 to remove and 21 not upgraded. Need to get 39.3 kB of archives. After this operation, 153 kB of additional disk space will be used. Get:1 http://archive.ubuntu.com/ubuntu xenial/universe amd64 jmtpfs amd64 0.5-2 [39.3 kB] Fetched 39.3 kB in 0s (62.2 kB/s) Selecting previously unselected package jmtpfs. (Reading database ... 417934 files and directories currently installed.) Preparing to unpack .../jmtpfs_0.5-2_amd64.deb ... Unpacking jmtpfs (0.5-2) ... Processing triggers for man-db (2.7.5-1) ... Setting up jmtpfs (0.5-2) ...