Dear Maintainer,


   * What led up to the situation?
When I turn OFF the monitor (to sleep), pulse audio re-selects HDMI output when I turn the monitor back ON (after a nap).

   * What exactly did you do (or not do) that was effective (or
     ineffective)?
I run pavucontrol to disable HDMI out (AGAIN).  Which then lets it select the previous ONLY "on" option for available devices.

   * What was the outcome of this action?
Sound on the intended device.

   * What outcome did you expect instead?
My sound routing preference to be kept, instead of changed when "other" devices toggle availability.

Apparently this also extends to power saving states, which I normally disable.

$ xset -dpms s noblank s noexpose

When NOT set this way, when the monitor powers off (inactivity) and back on with input (mouse movement / keyboard), it will change the audio routing to favor the HDMI of the monitor, not my usb audio interface attached to speakers. Solved by running pavucontrol to turn off the hdmi output (AGAIN).