In current-testing repo it is now available stubdomain with updated components including kernel, pulseaudio and QEMU (thanks to @fepitre). Quick testing shows much more clear sound with Windows and some VM performance improvements with USB attached devices.
@enmus if you see messages like this in dmesg log while attaching to Linux-based VMs than UAS is a problem. It might be possible to build guest VM kernel w/o UAS support to usb-storage driver instead for all USB storage devices.
[ +0.029211] usb 2-1: USB controller vhci_hcd.0 does not support streams, which are required by the UAS driver.
[ +0.000029] usb 2-1: Please try an other USB controller if you wish to use UAS.