Smartphone headset microphone not working, only internal does
Solution 1:
I have solved the problem. What I did to do so is I went to HDA Jack Retasking, selected Realtek codec, checked "Show unconnected pins" on the right panel, overrided Pin ID 0x18 & 0x19 with selection of Microphone, and applied settings on the bottom right.
After that, I went to pavucontrol > Input Devices and changed port to "Microphone (unplugged)":
and this actually solved my problem. Hope it helps someone! :)