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• I have searched the issues and this bug has not been reported previously

Describe the bug
On Fedora 41, I'm experiencing an issue on Quickemu 4.9.7 where guest VMs run under Quickemu crash when the guest tries to output audio.

I have narrowed this down to the fix in #1480, which attempts to fix an issue that another user was having when starting VMs on a host without PulseAudio installed.

The logic in the commit merged in #1480 involves using command -v to check whether the host has pacmd present before falling back to ALSA if the host does not.

I'm not sure this is the most sensible approach here as, if I understand it correctly, Fedora uses PipeWire as the primary audio server now, with compatibility layers for legacy PulseAudio applications. I think a lot of this is done by the pipewire-pulseaudio compatibility package which is installed by default on Fedora Workstation.

But what Fedora doesn't have installed by default is any package that provides pacmd. So Quickemu 4.9.7 on Fedora 41 (and maybe older) will always default to falling back to ALSA. And I'm not sure the backend plumbing is actually there anymore to handle this, so ultimately this means VMs simply crash whenever they first try and output any audio.

To Reproduce
Steps to reproduce the behaviour:

1. Run a Linux VM on Quickemu 4.9.7 on a stock Fedora Workstation 41.
2. Try to output some audio in the VM.
3. Experience the crash.
4. Revert the PR in fix: Use ALSA on systems without a PulseAudio daemon #1480 and repeat as above.
5. Experience no crash.

Expected behaviour
The test in #1480 should probably be rewritten not to make the assumption that any machine without pacmd cannot use PulseAudio as an output, to account for distros using PipeWire.

PR to follow with a suggested fix, though I'm open to discussion as it might not be the best overall method of handling things.