You may have noticed your plugged in headset shows up as “Headset (unplugged)” in Pavucontrol and it does not take audio input. Your computer is probably missing on some kernel modules for audio capture to work properly. Put the following in /etc/modprobe.d/alsa-base.conf

options snd-hda-intel model=alc255-acer,dell-headset-multi

These modules work even when your device is not from the said OEMs. Additionally, there might already exist a module specifically for your machine. In that case, put that in the file and reboot.