This repo contains a working version of the spotify x86-64 linux client packaged as an xdg-app. Unfortunately there is no redistribution rights for the spotify binaries, so you have to create your own to use it.
The package uses the freedesktop.org runtime, so you first need to install the sdk (so you can build the bundled stuff) and the platform:
wget https://sdk.gnome.org/keys/gnome-sdk.gpg
xdg-app --user remote-add --gpg-key=gnome-sdk.gpg gnome http://sdk.gnome.org/repo/
xdg-app --user install gnome org.freedesktop.Sdk 1.4
xdg-app --user install gnome org.freedesktop.Platform 1.4
To test this, do:
make
xdg-app --user remote-add --no-gpg-verify local-spotify repo
xdg-app --user install local-spotify com.spotify.Client