package lvm2 2.02.176-4.1ubuntu3 failed to install/upgrade: installed lvm2 package post-installation script subprocess returned error exit status 1 - "Possible missing firmware ... for module amdgpu"

Trying to clean up after a 16.04 -> 18.04 upgrade, I removed lvm2, which I'm honestly still not sure is necessary for LVM support, but resulted in many lines of the form during "processing of initramfs-tools":

W: Possible missing firmware /lib/firmware/amdgpu/vegam_smc.bin for module amdgpu

Not sure even if that's the main issue, but nothing else looks out of place. Here's a more complete transcript:

Setting up lvm2 (2.02.176-4.1ubuntu3) ...
update-initramfs: deferring update (trigger activated)
Failed to restart lvm2-lvmetad.service: Unit lvm2-lvmetad.socket is masked.
invoke-rc.d: initscript lvm2-lvmetad, action "restart" failed.
● lvm2-lvmetad.service - LVM2 metadata daemon
   Loaded: loaded (/lib/systemd/system/lvm2-lvmetad.service; static; vendor preset: enabled)
   Active: inactive (dead) since Sun 2018-10-21 14:50:29 EDT; 3min 29s ago
     Docs: man:lvmetad(8)
 Main PID: 512 (code=exited, status=0/SUCCESS)

Oct 21 14:50:29 monolith systemd[1]: Stopping LVM2 metadata daemon...
Oct 21 14:50:29 monolith systemd[1]: Stopped LVM2 metadata daemon.
dpkg: error processing package lvm2 (--configure):
 installed lvm2 package post-installation script subprocess returned error exit status 1
Processing triggers for initramfs-tools (0.130ubuntu3.5) ...
update-initramfs: Generating /boot/initrd.img-4.15.0-36-generic
W: Possible missing firmware /lib/firmware/amdgpu/vega12_gpu_info.bin for module amdgpu
W: Possible missing firmware /lib/firmware/amdgpu/vega12_asd.bin for module amdgpu
W: Possible missing firmware /lib/firmware/amdgpu/vega12_sos.bin for module amdgpu
W: Possible missing firmware /lib/firmware/amdgpu/vegam_rlc.bin for module amdgpu
W: Possible missing firmware /lib/firmware/amdgpu/vegam_mec2.bin for module amdgpu
W: Possible missing firmware /lib/firmware/amdgpu/vegam_mec.bin for module amdgpu
W: Possible missing firmware /lib/firmware/amdgpu/vegam_me.bin for module amdgpu
W: Possible missing firmware /lib/firmware/amdgpu/vegam_pfp.bin for module amdgpu
W: Possible missing firmware /lib/firmware/amdgpu/vegam_ce.bin for module amdgpu
W: Possible missing firmware /lib/firmware/amdgpu/vega12_rlc.bin for module amdgpu
W: Possible missing firmware /lib/firmware/amdgpu/vega12_mec2.bin for module amdgpu
W: Possible missing firmware /lib/firmware/amdgpu/vega12_mec.bin for module amdgpu
W: Possible missing firmware /lib/firmware/amdgpu/vega12_me.bin for module amdgpu
W: Possible missing firmware /lib/firmware/amdgpu/vega12_pfp.bin for module amdgpu
W: Possible missing firmware /lib/firmware/amdgpu/vega12_ce.bin for module amdgpu
W: Possible missing firmware /lib/firmware/amdgpu/vegam_sdma1.bin for module amdgpu
W: Possible missing firmware /lib/firmware/amdgpu/vegam_sdma.bin for module amdgpu
W: Possible missing firmware /lib/firmware/amdgpu/vega12_sdma1.bin for module amdgpu
W: Possible missing firmware /lib/firmware/amdgpu/vega12_sdma.bin for module amdgpu
W: Possible missing firmware /lib/firmware/amdgpu/vega12_uvd.bin for module amdgpu
W: Possible missing firmware /lib/firmware/amdgpu/vegam_uvd.bin for module amdgpu
W: Possible missing firmware /lib/firmware/amdgpu/vega12_vce.bin for module amdgpu
W: Possible missing firmware /lib/firmware/amdgpu/vegam_vce.bin for module amdgpu
W: Possible missing firmware /lib/firmware/amdgpu/vega12_smc.bin for module amdgpu
W: Possible missing firmware /lib/firmware/amdgpu/vegam_smc.bin for module amdgpu
Errors were encountered while processing:
 lvm2
Press Return to continue, 'q' followed by Return to quit.

ProblemType: Package
DistroRelease: Ubuntu 18.04
Package: lvm2 2.02.176-4.1ubuntu3
ProcVersionSignature: Ubuntu 4.15.0-36.39-generic 4.15.18
Uname: Linux 4.15.0-36-generic x86_64
ApportVersion: 2.20.9-0ubuntu7.4
AptOrdering:
 libreadline5:amd64: Install
 lvm2:amd64: Install
 NULL: ConfigurePending
Architecture: amd64
Date: Sun Oct 21 14:53:42 2018
ErrorMessage: installed lvm2 package post-installation script subprocess returned error exit status 1
InstallationDate: Installed on 2017-12-12 (313 days ago)
InstallationMedia: Ubuntu 16.04.3 LTS "Xenial Xerus" - Release amd64 (20170801)
Python3Details: /usr/bin/python3.6, Python 3.6.6, python3-minimal, 3.6.5-3ubuntu1
PythonDetails: /usr/bin/python2.7, Python 2.7.15rc1, python-minimal, 2.7.15~rc1-1
RelatedPackageVersions:
 dpkg 1.19.0.5ubuntu2
 apt 1.6.3ubuntu0.1
SourcePackage: lvm2
Title: package lvm2 2.02.176-4.1ubuntu3 failed to install/upgrade: installed lvm2 package post-installation script subprocess returned error exit status 1
UpgradeStatus: Upgraded to bionic on 2018-10-09 (12 days ago)