Lunar fix is attached.

Tested locally after downloading a lunar image:

$ autopkgtest initramfs-tools -- qemu autopkgtest-lunar-amd64.img
It uses the package in updates, therefore this fails:
Begin: Running /scripts/local-bottom ... done.
...
...
[   17.069410] Call Trace:
[   17.069504]  <TASK>
[   17.069594]  dump_stack_lvl+0x48/0x70
[   17.069747]  dump_stack+0x10/0x20
[   17.069866]  panic+0x37b/0x3c0
[   17.070029]  out_of_memory+0x36c/0x370
[   17.070226]  __alloc_pages_may_oom+0x112/0x1e0
[   17.070480]  __alloc_pages_slowpath.constprop.0+0x4c7/0xa20
[   17.070761]  __alloc_pages+0x31d/0x350
[   17.070992]  alloc_pages+0x90/0x1a0
[   17.071179]  __get_free_pages+0x11/0x50
[   17.071362]  pgd_alloc+0x20/0xc0
[   17.071548]  mm_init+0x18a/0x390
[   17.071730]  dup_mm.constprop.0+0x51/0x120
[   17.071933]  copy_process+0xae3/0x1570
[   17.072165]  kernel_clone+0xbd/0x440
[   17.072373]  __do_sys_clone+0x76/0xb0
[   17.072587]  __x64_sys_clone+0x25/0x40
[   17.072816]  do_syscall_64+0x5b/0x90
[   17.073027]  ? syscall_exit_to_user_mode+0x29/0x50
[   17.073269]  ? do_syscall_64+0x67/0x90
[   17.073446]  ? do_user_addr_fault+0x1e8/0x720
[   17.073654]  ? exit_to_user_mode_prepare+0x30/0xb0
[   17.073871]  ? irqentry_exit_to_user_mode+0x9/0x20
[   17.074089]  ? irqentry_exit+0x43/0x50
[   17.074322]  ? exc_page_fault+0x91/0x1b0
[   17.074474]  entry_SYSCALL_64_after_hwframe+0x72/0xdc
[   17.074723] RIP: 0033:0x7fb27d64be07
[   17.074897] Code: 00 66 90 f3 0f 1e fa 64 48 8b 04 25 10 00 00 00 45 31 c0 31 d2 31 f6 bf 11 00 20 01 4c 8d 90 d0 02 00 00 0
[   17.075588] RSP: 002b:00007ffc9dba5538 EFLAGS: 00000246 ORIG_RAX: 0000000000000038
[   17.075976] RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007fb27d64be07
[   17.076359] RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000001200011
[   17.076669] RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
[   17.077004] R10: 00007fb27d567a10 R11: 0000000000000246 R12: 0000000000000001
[   17.077354] R13: 0000556e56d9f5f0 R14: 0000556e56d9d798 R15: 0000000000000000
[   17.077722]  </TASK>
[   17.078438] Kernel Offset: 0x2c00000 from 0xffffffff81000000 (relocation range: 0xffffffff80000000-0xffffffffbfffffff)
[   17.079602] ---[ end Kernel panic - not syncing: System is deadlocked on memory ]---
qemu-system-x86_64: terminating on signal 15 from pid 7616 (timeout)
autopkgtest [14:15:54]: test net: -----------------------]
autopkgtest [14:15:55]: test net:  - - - - - - - - - - results - - - - - - - - - -
net                  FAIL non-zero exit status 124
autopkgtest [14:15:55]: @@@@@@@@@@@@@@@@@@@@ summary
amd64-klibc          PASS
amd64-busybox        PASS
amd64-ata-only       PASS
amd64-virtio-only    PASS
amd64-separate-usr   PASS
amd64-panic-shell    PASS
command1             PASS
net                  FAIL non-zero exit status 124
qemu-system-x86_64: terminating on signal 15 from pid 40557 (/usr/bin/python3)

$ autopkgtest ~/canonical/initramf-tools/initramfs-tools_0.142ubuntu3.dsc -- qemu autopkgtest-lunar-amd64.img 
This is the fix and the results are good:

net                  PASS
autopkgtest [14:32:26]: @@@@@@@@@@@@@@@@@@@@ summary
amd64-klibc          PASS
amd64-busybox        PASS
amd64-ata-only       PASS
amd64-virtio-only    PASS
amd64-separate-usr   PASS
amd64-panic-shell    PASS
command1             PASS
net                  PASS
qemu-system-x86_64: terminating on signal 15 from pid 46267 (/usr/bin/python3)