Today when I plugged in external speakers or earbuds into the audio jack
on my notebook, the sound no longer transfers from the built-in speakers
to the jack. The sound stops in the built-in speakers as expected but
it is not transferred to the jack.

If I run pavucontrol and choose "playback" I can see the volume meter
hopping around as the sounds are processed. Strangely, if I choose
"output devices, port: speakers (unavilable)" I can also see the volume
meter being active and if I choose "output devices, port: headphones
(plugged in)" then the volume meter goes completely motionless after
zeroing out. This is the opposite of what I expect. I had expected
that when I plug in the headphones to the audio jack that the sound
activity would be shown there.

I booted Linux Mint 19's Live image and the audio jack functions as
normal there so the problem seems to be with Devuan. I am open for
ideas about how to resolve this so that the audio jack may be used again.

/Lars

$ lsb_release -d; uname -r;
Description:    Devuan GNU/Linux 2.0 (ascii)
4.9.0-8-amd64