System theme not synchronising with desktop on KDE Plasma 6.6.5

Observed behaviour

It changed to dark, then back to light mode straight away.

Reproduction steps

Make sure you have Day Night Cycle enabled in Day Night Cycle settings and Switch to Dark Mode at Night enabled in Global Theme settings.
Open Fluxer app (must be using the .rpm or .deb version, Flatpak version won't be affected, but canary doesn't have a Flatpak version yet).
Wait for the desktop theme to change based on the time of the day.

Build information

Canary Desktop 2026.519.0, Web 2026.521.73431, Linux 6.19.14-300.fc44.x86_64 (x64), Electron 41.2.2, Chrome 146.0.7680.188, Node 24.14.1, Locale en-GB

Platform

Linux

Details

Expected behaviour It should change Fluxer's light theme to dark automatically with the system settings.