Created attachment 165175 [details] screenshot See attachment
Can reproduce. Does not affect the KScreen OSD, though.
Likely needs the same fix as Bug 472727.
Adding the "_kirigamiTheme" line as in https://bugs.kde.org/show_bug.cgi?id=472727 doesn't fix it. Interesting thing is: looks like the powerdevil OSD source code is modified from the kscreen OSD. I compared the two, and they are essentially the same, except missing the above line. I suspect the difference is in how they are launched: kscreen has a desktop file "org.kde.kscreen.desktop", powerdevil not.
A possibly relevant merge request was started @ https://invent.kde.org/plasma/powerdevil/-/merge_requests/354
Git commit 548e56201fa95f308fb98596cc3c9ce647f9b7fb by Nicolas Fella. Committed on 06/05/2024 at 14:12. Pushed by nicolasfella into branch 'master'. [osd] Force Plasma styling The OSD should follow the shell colors/styling, not the application styling M +2 -0 osd/osd.cpp https://invent.kde.org/plasma/powerdevil/-/commit/548e56201fa95f308fb98596cc3c9ce647f9b7fb
Git commit 839cce0cee203898b2b1d6715daeff50f0726872 by Nicolas Fella. Committed on 06/05/2024 at 14:20. Pushed by nicolasfella into branch 'Plasma/6.0'. [osd] Force Plasma styling The OSD should follow the shell colors/styling, not the application styling (cherry picked from commit 548e56201fa95f308fb98596cc3c9ce647f9b7fb) M +2 -0 osd/osd.cpp https://invent.kde.org/plasma/powerdevil/-/commit/839cce0cee203898b2b1d6715daeff50f0726872