Comment 9 for bug 1656289

I just tested on a clean system with:

$ apt-cache policy snapd snap-confine
snapd:
  Installed: 2.17.1ubuntu1
  Candidate: 2.20.1ubuntu1
  Version table:
     2.20.1ubuntu1 500
        500 http://us.archive.ubuntu.com/ubuntu xenial-updates/main amd64 Packages
 *** 2.17.1ubuntu1 100
        100 /var/lib/dpkg/status
     2.0.2 500
        500 http://us.archive.ubuntu.com/ubuntu xenial/main amd64 Packages
snap-confine:
  Installed: 1.0.43-0ubuntu1~16.04.1
  Candidate: 2.20.1ubuntu1
  Version table:
     2.20.1ubuntu1 500
        500 http://us.archive.ubuntu.com/ubuntu xenial-updates/main amd64 Packages
 *** 1.0.43-0ubuntu1~16.04.1 100
        100 /var/lib/dpkg/status

and installed the latest snap in edge (r21, ie the one with xenial libraries) and I see the snap is not using pulseaudio and instead preferring alsa:

ALSA lib conf.c:3750:(snd_config_update_r) Cannot access file /usr/share/alsa/alsa.conf
ALSA lib pcm.c:2266:(snd_pcm_open_noupdate) Unknown PCM plug:default

This does not appear to be a regression in snapd 2.17 vs 2.20.1. Downgrading the snap itself to r16 allows for sound to work with 2.17. Downgrading/reverting the snap itself to r16 with snapd and snap-confine 2.20.1 also allows sound to work.

It appears to be something in the snap that making it not use pulseaudio.