package lxd 3.0.3-0ubuntu1~18.04.1 failed to install/upgrade: new lxd package pre-installation script subprocess returned error exit status 1

I was trying a upgrade on a server from 18.04 to 20.04 but do-release-upgrade fails when trying to upgrade lxd as the SNAP content site has an expired/revoked certificate

The error in do-release-upgrade is

==> Installing the LXD snap from the 4.0 track for ubuntu-20.04
2021-10-15T15:34:39-04:00 INFO Waiting for automatic snapd restart...
error: cannot perform the following tasks:
- Download snap "core20" (1169) from channel "stable" (Get https://canonical-lcy
01.cdn.snapcraftcontent.com/download-origin/canonical-lgw01/DLqre5XGLbDqg9jPtiAh
RRjDuPVa5X1q_1169.snap?interactive=1&token=1634338800_2b7ac0f78ddb21e1b3760018c7
00fe9e99fd4e8f: x509: certificate signed by unknown authority)
dpkg: error processing archive /raid/scratch/apt-dpkg-install-FMjRvH/00-lxd_1%3a
0.9_all.deb (--unpack):
 new lxd package pre-installation script subprocess returned error exit status 1
ERROR: Cannot create report: [Errno 17] File exists: '/var/crash/lxd.0.crash'

And we can see the issue with a simple 'wget'

$ wget -O tmp.dpkg 'https://canonical-lcy01.cdn.snapcraftcontent.com/download-origin/canonical-lgw01/DLqre5XGLbDqg9jPtiAhRRjDuPVa5X1q_1169.snap?interactive=1&token=1634338800_2b7ac0f78ddb21e1b3760018c700fe9e99fd4e8f'
--2021-10-15 20:58:22-- https://canonical-lcy01.cdn.snapcraftcontent.com/download-origin/canonical-lgw01/DLqre5XGLbDqg9jPtiAhRRjDuPVa5X1q_1169.snap?interactive=1&token=1634338800_2b7ac0f78ddb21e1b3760018c700fe9e99fd4e8f
Resolving canonical-lcy01.cdn.snapcraftcontent.com... 91.189.88.179, 91.189.88.178
Connecting to canonical-lcy01.cdn.snapcraftcontent.com|91.189.88.179|:443... connected.
ERROR: The certificate of ‘canonical-lcy01.cdn.snapcraftcontent.com’ is not trusted.
ERROR: The certificate of ‘canonical-lcy01.cdn.snapcraftcontent.com’ has expired.

The whole upgrade then fails as lxd is a dependency and one is left with the server in a partial state

ProblemType: Package
DistroRelease: Ubuntu 20.04
Package: lxd 3.0.3-0ubuntu1~18.04.1
ProcVersionSignature: Ubuntu 5.4.0-87.98~18.04.1-generic 5.4.140
Uname: Linux 5.4.0-87-generic x86_64
NonfreeKernelModules: nvidia_modeset nvidia
ApportVersion: 2.20.11-0ubuntu27.20
Architecture: amd64
CasperMD5CheckResult: skip
Date: Fri Oct 15 15:34:43 2021
ErrorMessage: new lxd package pre-installation script subprocess returned error exit status 1
InstallationDate: Installed on 2020-08-11 (429 days ago)
InstallationMedia: Ubuntu-Server 18.04.4 LTS "Bionic Beaver" - Release amd64 (20200203.1)
Python3Details: /usr/bin/python3.8, Python 3.8.10, python3-minimal, 3.8.2-0ubuntu2
PythonDetails: /usr/bin/python2.7, Python 2.7.18, python-is-python2, 2.7.17-4
RelatedPackageVersions:
 dpkg 1.19.7ubuntu3
 apt 2.0.6
SourcePackage: lxd
Title: package lxd 3.0.3-0ubuntu1~18.04.1 failed to install/upgrade: new lxd package pre-installation script subprocess returned error exit status 1
UpgradeStatus: Upgraded to focal on 2021-10-15 (0 days ago)