I also tried to update using the update assistant installer and windows 20H2 ISO method, neither of them worked for me either and the installation failed. I don't have the know how to block the driver uninstall and block method. So I will be forced to wait
for a driver upday from Microsoft.
I'm trying to update an Asus K501UX, which is quite a high spec laptop, you would think the driver that windows gave you would be on the windows catalogue if it worked for another Asus machine!!
I did search for the "Conexant Media 8.66.95.70" driver on Windows update catalog but couldn't find anything there.
Then I googled and found a site that says it has the driver with the matching driver version 8.66.95.70 (dated 16 October 2020). Although any driver downloaded from a third-party site is not recommended, but I downloaded and installed it.
Surprisingly the Windows driver update section is no longer offering me this driver update.

This means It was indeed the one that I was offered before. To be sure I looked at my device manager section and I was right. It was indeed version 8.66.95.70 that got installed.

Now If anyone wants to try this that would have to do it at their own risk. I can't and do not recommend anyone to go and install any driver from a third-party website. But if you want here are the facts.
The link to the driver download page: https://www.drvhub.net/devices/sound-cards/synaptics/smartaudio-hd-1

also, see that RED ARROW that I have placed beside the Hardware ID names. Mine matched with the specified ones. You should match yours as well before trying it out. That way I think you'll have more chances of being successful.
How to find your Device Specific Hardware ID: just go to this "Details tab" and choose "Hardware ID" from the dropdown list.
Look for the "Underlined serial". Only this part varies from device to device. The rest of the ones are all same.

After download follow this guide to update the drive:
First, download the driver .zip file from the link above.
Use the "Download Driver" option, not the Big Greenish button that says "Install Driver" option because they will try to install their own software to install the driver. So don't use the "Install Driver" option".
Then extract the content of the .zip file in a separate folder. (You will need WinRar for this purpose). Next, follow these steps.
- Click the Update Driver.

- Click the Browse my computer for driver software option.

- Select the main folder with the downloaded driver content you have extracted earlier.
Don't forget to check the Include subfolders option.

- Click the Next.
Windows will search the folder and will install the drivers. After installation, you will be told to Restart. and then it's done.