You need to change the security setting before you install audio driver for Big Sur.
To change the security setting on your MacBook with the M1 chip, you need to go into macOS Recovery mode.
1. Turn on your MacBook holding the power button.
Click "Security Policy..." on Startup Security Utility".
If you do not see the Startup disk, follow the steps below.
2. Click "Continue of Options" and "Select a user you know the password for : " will appear.
Select your account and click Next. Then enter your password.
Select "Utilities" on the top left and select "Startup Security Utility".
Click "Unlock", enter your password and click "Security Policy...".
3. On the screen below, choose "Reduced Security", check "Allow user management of kernel extensions from identified developers" and click "OK".
4. Restart your MacBook and see if audio driver is correctly recognized.
Please refer to "important notice" when you install audio driver for Big Sur as well.