Headphones and speakers at the same time on my Thinkpad

like the title says, I can’t seem to auto-mute the speakers if I plug in my headphones. I’ve checked in alsamixer but it doesn’t even have a headphones section and I’ve tried the workaround posted here a couple of years ago adding the lines

alias snd-card-0 snd-hda-intel alias sound-slot-0 snd-hda-intel options snd-hda-intel model=dell-m4-1 enable_msi=1 

in the alsa-base.conf file but it didn’t work.