I have found a solution for this after a few hours of digging. Check out my post here: https://superuser.com/questions/1546739/keep-the-realtek-application-off-my-computer-in-windows-10-solution

(copied and pasted below for convenience)

Original post: Keep the Realtek application off my computer in Windows 10

Since I don't have enough rep to comment or answer, I figured I will explain how to actually do this.

Note: I am on a Dell G7 and these steps may be slightly different for your machine.

1. Use Add/Remove programs to uninstall the Realtek driver (if it exists)
2. Reboot
3. Let Windows install the drivers automatically from Windows update (to verify this, you should see your audio device working and showing up as Realtek)
4. Open Explorer and navigate to C:\Windows\System32\DriverStore\FileRepository (this is where Windows 10 keeps the driver update files)
5. Sort by Date modified, and you should see multiple folders modified very recently (there may be non-audio-related files here, so be careful)
6. Find all of the relevant folders for the audio drivers

in my case:

• hdxdellsstcsmb2018.inf_amd64_e3e1faa54cd2ea1c
• wavesapo.inf_amd64_043a570d84e7e965
• wavesapo75de.inf_amd64_5ff36f834a6d461a
• dellaudioextwaves.inf_amd64_a8fc1a4f86ac4fa9
• hdx_dellcsmbext_waves.inf_amd64_37d08961dc33a03e
• hdx_dellcsmbext_waves.inf_amd64_de3d27adc6ebf608
• hdxdellcsmb2018.inf_amd64_0cf5b01244c7b3dc
• realtekservice.inf_amd64_fcea3531959f3bc4
• realtekasio.inf_amd64_b061b3594ae23953
• realtekapo.inf_amd64_4748908cf13baa19

6. For each of these folders, follow the instructions by @Livven on the original post to change the inherited permissions: Keep the Realtek application off my computer in Windows 10 (note: I also had to change ownership to my user)
7. Go into each folder and delete all of the files inside them
8. Once complete, run Windows Update. It will complain that it cannot update the drivers because of permissions
9. Run the Microsoft “Show or Hide Updates” troubleshooter: https://support.microsoft.com/en-us/help/3073930/how-to-temporarily-prevent-a-driver-update-from-reinstalling-in-window
10. You should see the Realtek updates in the troubleshooter. Select them and hide them.
11. Reboot
12. Note: this step may be specific to Dell machines.

In order to get the Microsoft High Definition Audio Device to install and work properly, I had to install the Realtek driver from Dell's website for my machine. I then rebooted and uninstalled the Realtek driver. This switched my audio driver back to Microsoft's. I then rebooted again, and can confirm that Windows update will not automatically install the Realtek driver (because the folders are access restricted and the Show or Hide update troubleshoot has hid them).

Enjoy!

Edit: this should also cover Make Windows 10 stop installing driver software automatically

Note: I am on a Dell G7 and these steps may be slightly different for your machine.

1. Use Add/Remove programs to uninstall the Realtek driver (if it exists)
2. Reboot
3. Let Windows install the drivers automatically from Windows update (to verify this, you should see your audio device working and showing up as Realtek)
4. Open Explorer and navigate to C:\Windows\System32\DriverStore\FileRepository (this is where Windows 10 keeps the driver update files)
5. Sort by Date modified, and you should see multiple folders modified very recently (there may be non-audio-related files here, so be careful)
6. Find all of the relevant folders for the audio drivers

in my case:

• hdxdellsstcsmb2018.inf_amd64_e3e1faa54cd2ea1c
• wavesapo.inf_amd64_043a570d84e7e965
• wavesapo75de.inf_amd64_5ff36f834a6d461a
• dellaudioextwaves.inf_amd64_a8fc1a4f86ac4fa9
• hdx_dellcsmbext_waves.inf_amd64_37d08961dc33a03e
• hdx_dellcsmbext_waves.inf_amd64_de3d27adc6ebf608
• hdxdellcsmb2018.inf_amd64_0cf5b01244c7b3dc
• realtekservice.inf_amd64_fcea3531959f3bc4
• realtekasio.inf_amd64_b061b3594ae23953
• realtekapo.inf_amd64_4748908cf13baa19

6. For each of these folders, follow the instructions by @Livven on the original post to change the inherited permissions: Keep the Realtek application off my computer in Windows 10 (note: I also had to change ownership to my user)
7. Go into each folder and delete all of the files inside them
8. Once complete, run Windows Update. It will complain that it cannot update the drivers because of permissions
9. Run the Microsoft “Show or Hide Updates” troubleshooter: https://support.microsoft.com/en-us/help/3073930/how-to-temporarily-prevent-a-driver-update-from-reinstalling-in-window
10. You should see the Realtek updates in the troubleshooter. Select them and hide them.
11. Reboot
12. Note: this step may be specific to Dell machines.

In order to get the Microsoft High Definition Audio Device to install and work properly, I had to install the Realtek driver from Dell's website for my machine. I then rebooted and uninstalled the Realtek driver. This switched my audio driver back to Microsoft's. I then rebooted again, and can confirm that Windows update will not automatically install the Realtek driver (because the folders are access restricted and the Show or Hide update troubleshoot has hid them).

Enjoy!

Edit: this should also cover Make Windows 10 stop installing driver software automatically