I know this is old but we saw similar issues and pinning the CPU allowed you to move past the hung installing process. It did in our case.
Extract the OVMF_CODE_4M.fd file from Debian / Ubuntu ovmf package and put it in /usr/share/edk2-ovmf/OVMF_CODE_4M.fd
.
Override the LXD instance config with raw.qemu.conf
key like follows:
raw.qemu.conf: |-
[drive][0]
file = "/usr/share/edk2-ovmf/OVMF_CODE_4M.fd"