Without editing any, does it still start for you from the PrtScn key?
Asking since a rebuild is obviously needed, checking if it is just the .desktop file that needs adjusting (and subsequently will need an upstream bug report, if that fixes the issue).
Forget the above, this file
/usr/share/applications/org.kde.spectacle.desktop runs with just qdbus, will need qdbus-qt5 for KaOS, fix will be up shortly.
So it should read:
Exec=qdbus-qt5 org.kde.Spectacle / StartAgent