Greetings,
Welcome to the forum.
I am not a HP employee.
You should be able to disable onboard audio in the BIOS.
First, install the new audio card in the MB . Onboard audio cannot be disabled unless a discrete audio card is installed in the MB.
Boot to the BIOS. (F10).
Go to the Security Menu.
Select Device Security.
Disable System Audio.
Check Slot Security to ensure all PCIe slots are enabled.
Save and Exit the BIOS.
Install the driver for the new audio device.
The new audio device should now be visible in Windows Device Manager.
Regards