I've installed all the gstreamer plugins.
MTP and mtpfs are both working. I've successfully mounted
my phone to the computer.
I followed the guide on the ArchWiki for how to setup media
player support (using udev rules for my vendor).
On an interesting note, the example on the guide happens to be the
exact configuration I'm using since I'm on a Galaxy S4.
But anyways, after doing all this, Rhythmbox crashes when I go to
play music from the phone on it. It reads the phone successfully and
displays all the music on it. I can select a song. But when I press play
it freezes up.
Computers are extra dumb, which is why it takes extra smart people to make them work.
Did you try to see what happens when turning on debug messages with