cursor is always default size when mouse is over the desktop

Fresh install of Ubuntu 20.04, logged into a fresh KDE session. Increased the cursor size because I'm on a high res display, and noticed that when the mouse is over a window, the cursor size is correct, but when it's over the desktop, it's always the default (tiny) size. This makes it very hard to find on a virtual desktop with few application windows.

ProblemType: Bug
DistroRelease: Ubuntu 20.04
Package: plasma-workspace 4:5.18.5-0ubuntu0.1
ProcVersionSignature: Ubuntu 5.4.0-42.46-generic 5.4.44
Uname: Linux 5.4.0-42-generic x86_64
NonfreeKernelModules: zfs zunicode zavl icp zcommon znvpair nvidia_modeset nvidia
ApportVersion: 2.20.11-0ubuntu27.4
Architecture: amd64
CasperMD5CheckResult: skip
CurrentDesktop: KDE
Date: Thu Jul 23 22:48:41 2020
InstallationDate: Installed on 2020-07-15 (9 days ago)
InstallationMedia: Ubuntu 20.04 LTS "Focal Fossa" - Release amd64 (20200423)
SourcePackage: plasma-workspace
UpgradeStatus: No upgrade log present (probably fresh install)