To give more detail on the matter at hand:
-
$XDG_RUNTIME_DIRis set to /run/user/1000/snap.spotify inside the snap -
libpulsetries pulse socket locations in the following order:$XDG_RUNTIME_DIR/pulse/native,/var/run/pulse/native - pulse socket is not available in either location
Surprisingly it works on my system, the logs show that instead of trying $XDG_RUNTIME_DIR/pulse/native libpulse goes to {55f76458585f45adb352cdec85634ded}unix:/run/user/1000/pulse/native, as if $XDG_RUNTIME_DIR was completely ignored.