Comment 5 for bug 1772383

[No change - copying the file in the same dir adding .bak is sufficient right- or will this be read as a 2nd conf?]

adding .bak is ok, after reboot, you can run pactl list cards to verify if the change takes effect or not.
Before change:
       Profiles:
  output:analog-stereo-speaker: Speaker (sinks: 1, sources: 0, priority: 60, available: yes)
  output:analog-stereo-headphone+input:analog-stereo-mic: Headset (sinks: 1, sources: 1, priority: 80, available: yes)
  off: Off (sinks: 0, sources: 0, priority: 0, available: yes)

After change, the 1st two profiles disappear.

If the change takes effect, but it still can't work, I think it is not a pulseaudio issue, probably the firmware issue of dock or kernel driver issue.

And you can verify by these commands:

aplay -D plughw:CARD=xxx,DEV=0 test.wav (replace xxx with the name of usb audio card, aplay -L to check the name of usb audio card)
aplay -D plughw:CARD=xxx,DEV=1 test.wav

And BTW, what does "the vanilla ones from upstream" mean?