do-release-upgrade errors out because xscreensaver is the wrong version for lubuntu-desktop. Cannot remove/downgrade xscreensaver, so stuck in lubuntu 19.X

[Annoying One]

From /var/log/dist-upgrade/main.log:
2020-07-20 11:38:00,074 DEBUG Marking 'lubuntu-desktop' for upgrade
2020-07-20 11:38:01,181 WARNING Can't mark 'lubuntu-desktop' for upgrade (E:Unable to correct problems, you have held broken packages.)
2020-07-20 11:38:05,141 ERROR Dist-upgrade failed: 'Broken packages after upgrade: lubuntu-desktop'
2020-07-20 11:38:05,143 DEBUG abort called
2020-07-20 11:38:05,179 DEBUG openCache()
2020-07-20 11:38:19,336 DEBUG /openCache(), new cache size 92393

From /var/log/apt.log:
  Added xscreensaver:amd64 to the remove list
  Fixing lubuntu-desktop:amd64 via keep of xscreensaver:amd64
  Ignore MarkKeep of xscreensaver:amd64 < 5.42+dfsg1-1ubuntu1 @ii pgR > as its mode (Delete) is protected
Investigating (1) lubuntu-desktop:amd64 < 19.10.6 -> 20.04.8 @ii pumU Ib >
Broken lubuntu-desktop:amd64 Depends on xscreensaver:amd64 < 5.42+dfsg1-1ubuntu1 @ii pgR >
  Considering xscreensaver:amd64 5 as a solution to lubuntu-desktop:amd64 10000
  Added xscreensaver:amd64 to the remove list
  Fixing lubuntu-desktop:amd64 via keep of xscreensaver:amd64
  Ignore MarkKeep of xscreensaver:amd64 < 5.42+dfsg1-1ubuntu1 @ii pgR > as its mode (Delete) is protected
Investigating (2) lubuntu-desktop:amd64 < 19.10.6 -> 20.04.8 @ii pumU Ib >
Broken lubuntu-desktop:amd64 Depends on xscreensaver:amd64 < 5.42+dfsg1-1ubuntu1 @ii pgR >
  Considering xscreensaver:amd64 5 as a solution to lubuntu-desktop:amd64 10000
  Added xscreensaver:amd64 to the remove list
  Fixing lubuntu-desktop:amd64 via keep of xscreensaver:amd64
  Ignore MarkKeep of xscreensaver:amd64 < 5.42+dfsg1-1ubuntu1 @ii pgR > as its mode (Delete) is protected
Investigating (3) lubuntu-desktop:amd64 < 19.10.6 -> 20.04.8 @ii pumU Ib >
Broken lubuntu-desktop:amd64 Depends on xscreensaver:amd64 < 5.42+dfsg1-1ubuntu1 @ii pgR >
  Considering xscreensaver:amd64 10000 as a solution to lubuntu-desktop:amd64 10000
Done
Log time: 2020-07-20 11:38:18.207409

Before running do-release-upgrade, I ran apt-get update && apt-get upgrade, but nothing needed updating. I attempted to remove xscreensaver, but apt-get remove also wanted to remove lubuntu-desktop; this seemed like a bad idea, so I stopped that.

Release:
Description: Ubuntu 19.10
Release: 19.10

do-release-upgrade: version 19.10.15.4

Expected the upgrade to run to completion.
Upgrade exited with the above errors.

ProblemType: Bug
DistroRelease: Ubuntu 19.10
Package: ubuntu-release-upgrader-core 1:19.10.15.4
ProcVersionSignature: Ubuntu 5.3.0-62.56-generic 5.3.18
Uname: Linux 5.3.0-62-generic x86_64
ApportVersion: 2.20.11-0ubuntu8.9
Architecture: amd64
CrashDB: ubuntu
Date: Mon Jul 20 11:47:40 2020
InstallationDate: Installed on 2017-08-08 (1076 days ago)
InstallationMedia: Ubuntu 17.04 "Zesty Zapus" - Release amd64 (20170412)
PackageArchitecture: all
SourcePackage: ubuntu-release-upgrader
UpgradeStatus: Upgraded to eoan on 2020-07-20 (0 days ago)
VarLogDistupgradeAptclonesystemstate.tar.gz:
 Error: command ['pkexec', 'cat', '/var/log/dist-upgrade/apt-clone_system_state.tar.gz'] failed with exit code 127: polkit-agent-helper-1: pam_authenticate failed: Authentication failure
 Error executing command as another user: Not authorized

 This incident has been reported.