On Tue, 2 Jun 2020, Max wrote:
  However, the system decides that if the user plugs in
an USB soundcard
 the newly detected soundcard will be the new soundcard. :(
 In my case if I plug in a zoom H2_n recorder the desktop audio will be
 switched from the Jack Sink to the teeny speaker which is in that
 recorder. Not what is desirable.
 Is there a solution to this? 
The audio server you are talking about is PulseAudio. and yes that is the
way it works. solution:
pactl unload-module module-udev-detect
pactl unload-module module-alsa-card
Now use zita-ajbridge  to make your H2 recorder show or use jack_control
set up the h2 as master device and then SM. Sometimes jack_control sm
(switch master) works wonderfully time after time. Sometimes jack hangs at
that point and needs killall -9 jackdbus and a jack_control start.
--
Len Ovens
www.ovenwerks.net