After upgrading to Fedora 40 and Plasma 6, I’ve spent some time migrating Moe themes to Plasma 6 too. After finally switching to the new themes I couldn’t understand why the icons in system tray and restart/sleep are not changing.
Until I stumbled at this blog post How all this icon stuff is going to work in Plasma 6 – Adventures in Linux and KDE . It would be a nice thing to add a warning label either here Theme elements reference | Developer or here Understanding Plasma Styles | Developer