Code
<advancedsettings>
<videoscreen>
<monitor>Generic PnP Monitor #1</monitor>
</videoscreen>
</advancedsettings>
^ that content goes in /storage/.kodi/userdata/advancedsettings.xml (from https://forum.kodi.tv/showthread.php?tid=363060) but I have no idea what to replace "Generic PnP Monitor #1" with. Perhaps "HDMI-A-1" or have a look in kodi.log for the m_deviceName and m_displayName values logged for audio cards as I have a hunch it'll be based on EDID data.