I was first under the impression this could be related to a virus or malware, but even after refreshing with a clean Windows 10 installation, when I plug in my headset into the jack, the message comes to to choose what was plugged in (So the drivers are installed) And then I choose Headset (Over-ears) 

The line input is just one stereo jack, and it used to have worked. My mic picked up and the audio picked up on the mic.

But still the only mic active is the built-in mic on the laptop.

I have seen posts online that people say you go to: C:\Program Files\Realtek\Audio\HDA\RtkNGUI64.exe and under advanced you change settings there.

But the closest I have got is: C:\Program Files (x86)\Realtek\Audio
And in that folder I have Drivers & InstallShield

Nothing of use is located in InstallShield, and the one .exe in Drivers is: RtlUpd64.exe that does nothing when I run it.

I have also went to the support page on the DELL Support entered the service tag and downloaded the 1.05GB
That's this file: Realtek-High-Definition-Audio-Driver_TXHH9_WIN_6.0.9268.1_A05.EXE
When I run that setup it uninstalls all the Audio Driver and then wants to reboot.
After the reboot I have no drivers installed.

Then I run that file again, and nothing happens.
The box doesn't auto open when you plug in your headset eithers.

So now I have upgraded to Windows 11, and still is does the EXACT same thing.

It used to work fine, and now it doesn't anymore - even after a clean install. And all the Windows Updates have completed.

Under device Manager, if I update driver, there are no new updates found.