3 incorrectly shows “Headphones (unplugged)” even though ALSA output is unmuted [OO]
I suggest install alsa-tools and use jack detection tool to check the Headphone jack socket
sudo hdajacksensetest -c 0
If the Headphone jack detection is not working, use the jack retasking tool to disable jack detection
If jack-detection is disabled, KDE audio controls and pavucontrol should no longer show Headphone output as (unplugged)