Global themes displays the error after upgrade from plasma 5.
Could not load plugin from /nix/store/f53i4idyb5vbiqg11d421r4vs8hkwm0v-plasma-workspace-5.27.10/lib/qt-5.15.12/plugins/plasma/kcms/systemsettings/kcm_lookandfeel.so: The plugin ‘/nix/store/f53i4idyb5vbiqg11d421r4vs8hkwm0v-plasma-workspace-5.27.10/lib/qt-5.15.12/plugins/plasma/kcms/systemsettings/kcm_lookandfeel.so’ uses incompatible Qt library. (5.15.0) [release]