Comment 29 for bug 1873809

Trying to boot the proposed kernel in LXD:

"""
BdsDxe: loading Boot0007 "ubuntu" from HD(1,GPT,25633192-5DBD-412A-8A50-E29B79F72A50,0x800,0x32000)/\EFI\ubuntu\shimx64.efi
BdsDxe: starting Boot0007 "ubuntu" from HD(1,GPT,25633192-5DBD-412A-8A50-E29B79F72A50,0x800,0x32000)/\EFI\ubuntu\shimx64.efi
RAMDISK: incomplete write (4194304 != 8388608)
Kernel panic - not syncing: VFS: Unable to mount root fs on unknown-block(0,0)
CPU: 0 PID: 1 Comm: swapper/0 Not tainted 5.4.0-1017-kvm #17-Ubuntu
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009)/LXD, BIOS 0.0.0 02/06/2015
Call Trace:
 0xffffffff9392230d
 0xffffffff932a8a21
 0xffffffff9412e5c1
 0xffffffff9412e80f
 0xffffffff9412e976
 0xffffffff9412e274
 ? 0xffffffff93938a70
 0xffffffff93938a79
 0xffffffff93a00215
Kernel Offset: 0x12200000 from 0xffffffff81000000 (relocation range: 0xffffffff80000000-0xffffffffbfffffff)
---[ end Kernel panic - not syncing: VFS: Unable to mount root fs on unknown-block(0,0) ]---
"""

This appears to be lz4 related. Changing the initramfs to gzip makes the VM boot just fine.
It's worth noting that when booting the generic kernel, we get the unpack error showed in https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1835660 but things still boot fine.

Marking verification as failed based on this. We need images to work properly with a standard Ubuntu config so need lz4 fixed.