Raised with Quickemu project (https://github.com/quickemu-project/quickemu/issues/680) but it seems that on a lunar host 16.04 qemu vms may cease to work and/or fail to be installable because they can no longer see their virtual disk.
Raised from a physical installation on laptop but then investigated using Quickemu lunar vm ( installed from daily but then kept up-to-date during explorations).
The lunar VM had no problems installing later Ubuntus or current Debian and OpenSUSE Tumbleweed, and 16.04.7 experienced no issues installing on a host running 22.04 or 23.10.
On lunar you can boot the 16.04.7 iso and run a live VM, but installing from there or the installation option from boot progresses fine right up to selecting a disk, when it sees none ...
This also reported upstream (https://github.com/canonical/ubuntu-desktop-installer/issues/1760)
The actual issue, I suspect, will be some change relating to lunar's qemu-system and the kernel/disk device stack on 16.04.7
the qemu 16.04 VM is started with
/usr/bin/qemu-system-x86_64 -name ubuntu-16.04,process=ubuntu-16.04 -pidfile ubuntu-16.04/ubuntu-16.04.pid -enable-kvm -machine q35,smm=off,vmport=off -cpu host,kvm=on,topoext -smp cores=4,threads=2,sockets=1 -m 8G -device virtio-balloon -vga none -device virtio-vga-gl,xres=1664,yres=936 -display sdl,gl=on -audiodev pa,id=audio0 -device intel-hda -device hda-duplex,audiodev=audio0 -rtc base=localtime,clock=host,driftfix=slew -device virtio-rng-pci,rng=rng0 -object rng-random,id=rng0,filename=/dev/urandom -device qemu-xhci,id=spicepass -chardev spicevmc,id=usbredirchardev1,name=usbredir -device usb-redir,chardev=usbredirchardev1,id=usbredirdev1 -chardev spicevmc,id=usbredirchardev2,name=usbredir -device usb-redir,chardev=usbredirchardev2,id=usbredirdev2 -chardev spicevmc,id=usbredirchardev3,name=usbredir -device usb-redir,chardev=usbredirchardev3,id=usbredirdev3 -device pci-ohci,id=smartpass -device usb-ccid -chardev spicevmc,id=ccid,name=smartcard -device ccid-card-passthru,chardev=ccid -device usb-ehci,id=input -device usb-kbd,bus=input.0 -k en-us -device usb-tablet,bus=input.0 -device virtio-net,netdev=nic -netdev user,hostname=ubuntu-16.04,hostfwd=tcp::22221-:22,smb=/home/phil/Public,id=nic -global driver=cfi.pflash01,property=secure,value=on -drive if=pflash,format=raw,unit=0,file=/usr/share/OVMF/OVMF_CODE.fd,readonly=on -drive if=pflash,format=raw,unit=1,file=ubuntu-16.04/OVMF_VARS.fd -drive media=cdrom,index=0,file=ubuntu-16.04/ubuntu-16.04.7-desktop-amd64.iso -device virtio-blk-pci,drive=SystemDisk -drive id=SystemDisk,if=none,format=qcow2,file=ubuntu-16.04/disk.qcow2 -fsdev local,id=fsdev0,path=/home/phil/Public,security_model=mapped-xattr -device virtio-9p-pci,fsdev=fsdev0,mount_tag=Public-phil -monitor unix:ubuntu-16.04/ubuntu-16.04-monitor.socket,server,nowait -serial unix:ubuntu-16.04/ubuntu-16.04-serial.socket,server,nowait
and the qcow2 virtual disk appears fine to the lunar host as a 16G empty disk
Closing that ubuntu-