We're running into this issue with ALL of our Optiplex 9020s after the Windows 10 1803 update.
The RealTek driver (either from Dell or RealTek) will NOT install. It errors out, either with a -0001 error, or a 0x0000374 error.
The work-around, we've found, is to install the generic audio driver from Microsoft. We've noticed no adverse effects from using this driver.
Steps to do this in Windows 10:
1. Open the device manager
2. Find the Realtek HD Audio Controller (may be listed as an unknown device). It will likely have a yellow triangle next to it.
3. Right-click on the device and select "Update Driver"
4. Select "Browser my computer for driver software"
5. Select "Let me pick from a list of available drivers on my computer"
6. In the next window, you may be prompted for the TYPE of device. If you are, select "Sound, video and game controllers"
7. Ignore any RealTek drivers and select "High Definition Audio Device" and click NEXT.
This will install the generic Microsoft audio drivers, which seem to work after the 1803 and 1809 updates.