How to set an HDMI output to audio only, or prevent things from going to that display tied to that output?

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I have an HDMI output that is connected to an audio receiver but not an actual display. How do I either tell windows that there is no display and that this is an audio only port, or prevent my mouse and windows from going to the display that windows creates for this output?Mirroring displays is not an option. My actual screens are 4k 60hz and 4k 144hz. When I select mirror it limits the mirror to 1080p 60hz, so the mirrored display runs at 1/4 resolution. Setting "disconnect this display" is also not an option as that disables audio.

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