If the line in option still doesn't appear, it's possible that the Realtek update has caused a conflict or removed the option entirely. In this case, you can try rolling back the Realtek driver to the previous version. To do this:
* Open the Device Manager by right-clicking on the Start button and selecting "Device Manager" from the menu.
* Locate the "Sound, video and game controllers" section and expand it.
* Right-click on the Realtek audio device and select "Properties."
* In the Properties window, go to the "Driver" tab and click on the "Roll Back Driver" button. Follow the on-screen instructions to complete the process.