Comment 26 for bug 591823

I got this same warning:

$ sudo apt autoremove
Reading package lists... Done
Building dependency tree
Reading state information... Done
The following packages will be REMOVED
  linux-headers-5.4.0-66-lowlatency linux-headers-5.4.0-73-lowlatency linux-hwe-5.4-headers-5.4.0-66
  linux-hwe-5.4-headers-5.4.0-73 linux-image-5.4.0-66-lowlatency linux-image-5.4.0-73-lowlatency
  linux-modules-5.4.0-66-lowlatency linux-modules-5.4.0-73-lowlatency
0 to upgrade, 0 to newly install, 8 to remove and 0 not to upgrade.
After this operation, 714 MB disk space will be freed.
Do you want to continue? [Y/n]
(Reading database ... 492639 files and directories currently installed.)
Removing linux-headers-5.4.0-66-lowlatency (5.4.0-66.74~18.04.2) ...
Removing linux-headers-5.4.0-73-lowlatency (5.4.0-73.82~18.04.1) ...
Removing linux-hwe-5.4-headers-5.4.0-66 (5.4.0-66.74~18.04.2) ...
Removing linux-hwe-5.4-headers-5.4.0-73 (5.4.0-73.82~18.04.1) ...
Removing linux-image-5.4.0-66-lowlatency (5.4.0-66.74~18.04.2) ...
/etc/kernel/postrm.d/initramfs-tools:
update-initramfs: Deleting /boot/initrd.img-5.4.0-66-lowlatency
/etc/kernel/postrm.d/zz-update-grub:
Sourcing file `/etc/default/grub'
Generating grub configuration file ...
Found linux image: /boot/vmlinuz-5.4.0-77-lowlatency
Found initrd image: /boot/initrd.img-5.4.0-77-lowlatency
Found linux image: /boot/vmlinuz-5.4.0-74-lowlatency
Found initrd image: /boot/initrd.img-5.4.0-74-lowlatency
Found linux image: /boot/vmlinuz-5.4.0-73-lowlatency
Found initrd image: /boot/initrd.img-5.4.0-73-lowlatency
done
Removing linux-image-5.4.0-73-lowlatency (5.4.0-73.82~18.04.1) ...
/etc/kernel/postrm.d/initramfs-tools:
update-initramfs: Deleting /boot/initrd.img-5.4.0-73-lowlatency
/etc/kernel/postrm.d/zz-update-grub:
Sourcing file `/etc/default/grub'
Generating grub configuration file ...
Found linux image: /boot/vmlinuz-5.4.0-77-lowlatency
Found initrd image: /boot/initrd.img-5.4.0-77-lowlatency
Found linux image: /boot/vmlinuz-5.4.0-74-lowlatency
Found initrd image: /boot/initrd.img-5.4.0-74-lowlatency
File descriptor 10 (/var/lib/dpkg/triggers/linux-update-5.4.0-66-lowlatency (deleted)) leaked on lvs invocation. Parent PID 12476: /bin/sh
done
Removing linux-modules-5.4.0-66-lowlatency (5.4.0-66.74~18.04.2) ...
Removing linux-modules-5.4.0-73-lowlatency (5.4.0-73.82~18.04.1) ...

$ lsb_release -a
LSB Version: core-9.20170808ubuntu1-noarch:printing-9.20170808ubuntu1-noarch:security-9.20170808ubuntu1-noarch
Distributor ID: Ubuntu
Description: Ubuntu 18.04.5 LTS
Release: 18.04
Codename: bionic

I would guess this is actually a bug in grub-probe.