Allow selection of specific host audio input devices

I was hoping to send a mix of microphone and speaker audio to a VM, by using software on the host to create a virtual audio input device.

Unfortunately, UTM doesn't seem to have a way to choose which audio device a VM should capture from, so I can't make it capture from that loopback device. I can't set that as my default device, because then I'd get an echo or a feedback loop or such.

I'd greatly appreciate there being a way to pick which audio input device to use. For my uses, a single selection for the whole UTM application would be enough, but it would be even better for it to be per-VM.

My machine: M1 Max, MacOS 15.5, UTM 4.5.4.