kde – How to apply a color theme universally in Kubuntu 21.04

In Kubuntu 21.04, how can I apply a color theme so that it affects all (or at least most) components of the desktop?

In the Settings, I went to Appearance -> Colors -> edit theme button -> Common Colors, where I changed the selection background, along with the focus and hover decorations.

This affects most programs, but not the highlights in the panel nor the selection of desktop icons. In the screenshot I set the highlight color to pink, which is shown in the Settings window and file manager, but the default blue of the Breeze theme remains in the panel and desktop.

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Restarting those components does not do anything. This does work correctly in the older Kubuntu 20.04, and it’s not an issue in KDE Neon (I upgraded Plasma in Kubuntu via backports to see if that would fix it, but it does not).