package linux-image-unsigned-5.8.0-41-generic 5.8.0-41.46~20.04.1 failed to install/upgrade: run-parts: /etc/kernel/header_postinst.d/dkms exited with return code 4

[Franki Cheung]

tried to install rtl8841CU driver for my usb wifi adapter with dkms as upgrading to new linux header will break my static driver. Tried rolling back to 5.8.0-40 also caused such an error.

ProblemType: Package
DistroRelease: Ubuntu 20.04
Package: linux-image-unsigned-5.8.0-41-generic 5.8.0-41.46~20.04.1
ProcVersionSignature: Ubuntu 5.8.0-40.45~20.04.1-generic 5.8.18
Uname: Linux 5.8.0-40-generic x86_64
ApportVersion: 2.20.11-0ubuntu27.14
Architecture: amd64
CasperMD5CheckResult: skip
Date: Sat Jan 30 18:30:00 2021
ErrorMessage: run-parts: /etc/kernel/header_postinst.d/dkms exited with return code 4
InstallationDate: Installed on 2021-01-16 (13 days ago)
InstallationMedia: Ubuntu 20.04 LTS "Focal Fossa" - Release amd64 (20200423)
Python3Details: /usr/bin/python3.8, Python 3.8.5, python3-minimal, 3.8.2-0ubuntu2
PythonDetails: N/A
RelatedPackageVersions:
 dpkg 1.19.7ubuntu3
 apt 2.0.4
SourcePackage: dkms
Title: package linux-image-unsigned-5.8.0-41-generic 5.8.0-41.46~20.04.1 failed to install/upgrade: run-parts: /etc/kernel/header_postinst.d/dkms exited with return code 4
UpgradeStatus: No upgrade log present (probably fresh install)