Hi Rezaul_K,
Thank you for all of your help and I am happy to state that my system is now at Windows 10 Pro 20H2 with the sound working! Your help was invaluable. Here was my experience: I had not seen your update, but this morning upon booting up; my system appeared to have applied an experience update. However the Windows version was still showing version 1909. So I am not sure what that was about. After running Windows update twice, on the second run it gave me the option to download and apply 20H2 (not 2004)! I did it. Upon completion of the 20H2 update and a few reboots, the sound was still not working and I was still getting the policy restriction error when I tried to update the driver as mentioned. I went in and deleted the DeviceInstall key and all subkeys I had put in as per your instructions. Rebooted. Went to Device Manager and ran Update Driver on the "Other Device", it discovered and installed the Conexant driver, rebooted again.... and then boom, the sound is all good now!
I think my misunderstanding was that I thought that by restricting the Conexant audio device update via the registry, Windows would have automatically installed the Generic Windows Audio Driver being talked about and I would have sound. I also thought that after applying the 20H2 update, the registry entry restricting the device update would have been automatically removed. I must have misunderstood and made a few wrong assumptions.
I am still not sure if I skipped update 2004 or I just missed noticing it getting applied.
NOTE TO OTHERS: While I only had a day without my laptop's internal speakers working, I was able to have sound via a Bluetooth speaker and Bluetooth headphones. So I was never completely without sound.
I immediately came here to give you the good news and I found that you had already responded with a fix as well. Thank you for the quick response!
First of all, I am glad that I could be of help. I myself had gotten help from the Microsoft community as you did.
I want to clear up something here.
You suspecting whether you skipped upgrading to the 2004 version is; Yes, you did. As 20H2 is out now, and it being the latest update available (in reality it's an extended version of the 2004 version with some features added) Microsoft will offer it to anyone trying to upgrade from 1909 or any older build version of Windows 10.
About you getting an Experience update; Yes it's kind of a newer thing starting from the 2004 version (I believe before it was exclusively available only in the Developer Preview Build, not on Public Stable Builds. We are on Public Stable Builds). If you go to Settings (Win 10 new Settings panel) > System > About; down at the bottom within "Windows Specification" you will see the Feature Experience version. I myself have searched for this but couldn't find anything explaining what it is. Even Microsoft is vague about explaining it. But I think we don't have to be worried about this.
The whole point of the Registry Blocking method was to prevent Windows Update from automatically Updating/Re-installing the Conexant Device Drivers that we have chosen to Uninstall; the only incompatibility that prevented us from getting the new 2004/20H2 upgrade.
About you without a working internal/built-in audio; It was only because there was no driver to route any audio output via the audio combo 3.5mm headphone port.
Finally, I am glad that you have managed to solve the issue by urself.
Cheers 👍