Created attachment 179623 [details]
Screenshot of a bug with console errors shown

SUMMARY
In Window Rules settings all strings in dropdowns are missing. Some options are properly selectable despite this, but f.e. "Window types" setting can only uncheck one option, and it is not possible to know which option has been unchecked. 
When run through console, clicking on dropdowns is printing qml errors like
"
qrc:/kcm/kcm_kwinrules/OptionsComboBox.qml:88: ReferenceError: bitMask is not defined
qrc:/kcm/kcm_kwinrules/OptionsComboBox.qml:115:13: Unable to assign [undefined] to QString
qrc:/kcm/kcm_kwinrules/OptionsComboBox.qml:116: TypeError: Cannot read property 'length' of undefined
"
This makes the Windows Rules setting unusable.

STEPS TO REPRODUCE
1. Open KDE System settings
2. Go to Window Management > Window Rules
3. Edit or create a new rule

OBSERVED RESULT
All dropdowns will have missing strings when clicked. Dropdowns with checkboxes are unusable.

EXPECTED RESULT
All dropdowns should contain strings. Dropdowns with checkboxes should be able to check options properly.

SOFTWARE/OS VERSIONS
Operating System: Arch Linux 
KDE Plasma Version: 6.3.3
KDE Frameworks Version: 6.12.0
Qt Version: 6.8.2
Kernel Version: 6.13.7-arch1-1 (64-bit)
Graphics Platform: Wayland
Processors: 24 × AMD Ryzen 9 5900X 12-Core Processor
Memory: 62.7 GiB of RAM
Graphics Processor: AMD Radeon RX 6600
Manufacturer: Micro-Star International Co., Ltd.
Product Name: MS-7A38
System Version: 6.0

ADDITIONAL INFORMATION
I've encountered this bug using Plasma 6.3.3 and Frameworks 6.12 on Arch Linux and on Fedora 41.