Manual updates blocked by unattended-upgrade

Observed behaviour:

When I boot my PC or wake it from suspend, it usually gives a desktop notification about available updates.
Trying to apply the updates often results in this kind of error:

E: Could not get lock /var/lib/dpkg/lock-frontend. It is held by process 3522905 (unattended-upgr)

lsb_release -rd
No LSB modules are available.
Description: Ubuntu 23.04
Release: 23.04

Desired behaviour: have these two play nice with each other.

ProblemType: Bug
DistroRelease: Ubuntu 23.04
Package: unattended-upgrades 2.9.1+nmu2ubuntu2
ProcVersionSignature: Ubuntu 6.2.0-23.23-generic 6.2.12
Uname: Linux 6.2.0-23-generic x86_64
ApportVersion: 2.26.1-0ubuntu2
Architecture: amd64
CasperMD5CheckResult: unknown
CurrentDesktop: KDE
Date: Fri Jun 23 14:02:24 2023
InstallationDate: Installed on 2021-02-06 (866 days ago)
InstallationMedia: Kubuntu 20.04 LTS "Focal Fossa" - Release amd64 (20200423)
PackageArchitecture: all
SourcePackage: unattended-upgrades
UpgradeStatus: Upgraded to lunar on 2023-04-23 (61 days ago)
modified.conffile..etc.apt.apt.conf.d.10periodic:
 APT::Periodic::Update-Package-Lists "1";
 APT::Periodic::Download-Upgradeable-Packages "1";
 APT::Periodic::AutocleanInterval "0";
 APT::Periodic::Unattended-Upgrade "1";
mtime.conffile..etc.apt.apt.conf.d.10periodic: 2023-04-23T13:43:35.349235