package initramfs-tools 0.122ubuntu8.1 failed to install/upgrade: subprocess installed post-installation script returned error exit status 1

[Valiant Bear]

Very similar to other bugs, may be the same. I added a new one due to the 0.122ubuntu8.1 vice just ubuntu8 bit. I have no idea what any of this means, just trying to be helpful if it is a new bug...
Information I think might be important:
I was running Ubuntu Server 16.04 on a Raspberry Pi 3B+. The pi has an SD card with BerryBoot on it, and Ubuntu Server was installed on an external USB Hard Drive. I ran "do-release-upgrade" as recommended by the prompt after logging in, as it stated Ubuntu 18.04 was available. The upgrade process appeared to be running smoothly until I received an error that the root device could not be found. I was given Ctrl-C or Enter to Continue options, and I pushed enter. The initramfs bug I am reporting came after that. Not sure if they are related or not...

ProblemType: Package
DistroRelease: Ubuntu 16.04
Package: initramfs-tools 0.122ubuntu8.1
Uname: Linux 4.14.67v7-aufs armv7l
ApportVersion: 2.20.1-0ubuntu2.1
Architecture: armhf
Date: Fri Sep 7 21:31:02 2018
ErrorMessage: subprocess installed post-installation script returned error exit status 1
PackageArchitecture: all
RelatedPackageVersions:
 dpkg 1.18.4ubuntu1.1
 apt 1.2.12~ubuntu16.04.1
SourcePackage: initramfs-tools
Title: package initramfs-tools 0.122ubuntu8.1 failed to install/upgrade: subprocess installed post-installation script returned error exit status 1
UpgradeStatus: Upgraded to xenial on 2018-09-07 (0 days ago)

[Timo Aaltonen (tjaalton)]

Processing triggers for initramfs-tools (0.122ubuntu8.1) ...
update-initramfs: Generating /boot/initrd.img-4.4.0-1017-raspi2
WARNING: missing /lib/modules/4.4.0-1017-raspi2
Ensure all necessary drivers are built into the linux image!
depmod: ERROR: could not open directory /lib/modules/4.4.0-1017-raspi2: No such file or directory
depmod: FATAL: could not search modules: No such file or directory
cryptsetup: WARNING: could not determine root device from /etc/fstab
Warning: root device does not exist

Press Ctrl-C to abort build, or Enter to continue

W: mdadm: /etc/mdadm/mdadm.conf defines no arrays.
W: mkconf: MD subsystem is not loaded, thus I cannot scan for arrays.
W: mdadm: failed to auto-generate temporary mdadm.conf file.
depmod: WARNING: could not open /var/tmp/mkinitramfs_qsoaTD/lib/modules/4.4.0-1017-raspi2/modules.order: No such file or directory
depmod: WARNING: could not open /var/tmp/mkinitramfs_qsoaTD/lib/modules/4.4.0-1017-raspi2/modules.builtin: No such file or directory
Unsupported platform.
run-parts: /etc/initramfs/post-update.d//flash-kernel exited with return code 1
dpkg: error processing package initramfs-tools (--configure):
 subprocess installed post-installation script returned error exit status 1