I've encountered similar issues with older hardware, including sound cards like the CMI8738, when upgrading to a new OS like Windows 10. It seems that as newer versions of Windows come out, support for legacy hardware becomes more sparse, which can be frustrating.
Firstly, if you haven’t already tried it, I recommend searching for drivers on the official websites or popular driver repositories that focus on legacy hardware. Sometimes, websites like Station Drivers or DriverGuide can have more up-to-date community-uploaded drivers that might just work for you.
In my experience, what worked for me in a similar situation was to try using compatibility mode. You might already know this, but you can right-click the driver installation file, go to Properties, and from there select the Compatibility tab. Choose an older version of Windows like Windows 7 or 8 where the driver was originally meant to work. This can sometimes trick the installation process into thinking it's running on an older OS, and get those drivers working.
Another approach is using generic drivers provided by Windows. Although these won’t give you access to all the advanced features the card might have, they can sometimes at least get the basic audio functionality working. To do this, go into your Device Manager, find your sound card, and select “Update Driver”. Choose the option to browse your computer for drivers, then let Windows pick from its list – it may suggest something generic that can help in a pinch.
If all else fails, there's always the possibility of using an external USB sound card. They are relatively inexpensive and can serve as a stop-gap solution in situations like this.
Also, just a quick check: make sure to disable any on-board audio from your BIOS if it's still enabled, as this can sometimes cause conflicts with newly installed sound cards.
Have you tried any other solutions, or considered reaching out to any community forums that focus particularly on retro hardware? Sometimes those niche communities have brilliant solutions for getting old hardware to work in modern environments. Let me know how it goes, or if there are any other aspects you might want to tackle!
