Thanks for the prompt fix! In case you haven't noticed yet: qemu has backed out the move of the helper binaries. From the recent qemu changelog:
qemu (1:9.1.0+ds-3) unstable; urgency=medium * revert the move of the helper binaries (qemu-bridge-helper, virtfs-proxy-helper, vhost-user-gpu) to /usr/libexec/qemu/, moving them back to /usr/lib/qemu/ where they had always been. This restores suid-root dpkg-statoverride for qemu-bridge-helper if the user enabled it, and makes common tools like libvirt to work correctly again. Such change needs more thinking. Closes: #1080456. Not sure whether you'd like to back out the fix for this bug as well. Sorry for the hassle.