KDE (6.6.1 Neon) Desktop folder settings, Wallpaper
Wallpaper type: Image
“Switch dynamic wallpapers” sub-options suggests that there may be at least 2 images which will be used based on light/dark theme/style (one of the options reads “style” but on the System settings/Quick Settings you call Breeze as a “theme”), but the page does not make it apparent how to choose image for light and for dark or how it will be selected.