Pulseaudio disables auto mute, so speaker sound continues when headphones plugged in

[Boris Gjenero]

My Dell Inspiron 6400 laptop has HDA Intel audio with a STAC9200 codec. It has speakers and a headphone jack. Previously when the headphone jack was unplugged sound came from the speakers, and when headphones were plugged in, sound came only from the headphones. In Ubuntu 22.04, when I plug in the headphones, sound comes from both the speakers and headphones.

ALSA has the "Auto-Mute" feature, which mutes the speakers when headphones are plugged in. The problem is that Pulseaudio disables this feature. Every time I plug in headphones, I need to again re-enable that feature using alsamixer to stop sound from speakers.

The problem seems to be this unfixed bug in Pulseaudio: https://gitlab.freedesktop.org/pulseaudio/pulseaudio/-/issues/1297

ProblemType: Bug
DistroRelease: Ubuntu 22.04
Package: pulseaudio 1:15.99.1+dfsg1-1ubuntu1
ProcVersionSignature: Ubuntu 5.15.0-25.25-generic 5.15.30
Uname: Linux 5.15.0-25-generic x86_64
NonfreeKernelModules: wl
ApportVersion: 2.20.11-0ubuntu80
Architecture: amd64
AudioDevicesInUse:
 USER PID ACCESS COMMAND
 /dev/snd/controlC0: bgjenero 15920 F.... pulseaudio
CasperMD5CheckResult: unknown
CurrentDesktop: XFCE
Date: Wed Apr 13 00:57:54 2022
SourcePackage: pulseaudio
UpgradeStatus: Upgraded to jammy on 2022-04-04 (8 days ago)
dmi.bios.date: 06/13/2007
dmi.bios.release: 1.7
dmi.bios.vendor: Dell Inc.
dmi.bios.version: A17
dmi.board.name: 0XD720
dmi.board.vendor: Dell Inc.
dmi.chassis.type: 8
dmi.chassis.vendor: Dell Inc.
dmi.ec.firmware.release: 1.7
dmi.modalias: dmi:bvnDellInc.:bvrA17:bd06/13/2007:br1.7:efr1.7:svnDellInc.:pnMM061:pvr:rvnDellInc.:rn0XD720:rvr:cvnDellInc.:ct8:cvr:sku:
dmi.product.name: MM061
dmi.sys.vendor: Dell Inc.