SUMMARY

Modifier keys are not respected when using a tablet pen.
Performing actions that require a modifier key, such as Control + Click, act as if no modifier keys are pressed.

STEPS TO REPRODUCE
1. Use a tablet pen
2. Perform an action that uses both the pen and a modifier key. Eg control + click for multi-select

OBSERVED RESULT
Modifier keys are not respected. For example the following actions are impossible:
- Selecting multiple files in Dolphin using shift/control + click
- Opening a new instance of an application by shift-clicking it's icon in the task manager
- Drawing angled lines by holding shift/control in KolourPaint
- Selecting multiple emails in Kmail using shift/control + click

EXPECTED RESULT
Modifier keys function exactly as when using a mouse or touchscreen

SOFTWARE/OS VERSIONS
Operating System: Fedora Linux 40
KDE Plasma Version: 6.0.5
KDE Frameworks Version: 6.2.0
Qt Version: 6.7.1
Kernel Version: 6.8.11-300.fc40.x86_64 (64-bit)
Graphics Platform: Wayland
Processors: 16 × Intel® Core™ i9-9900K CPU @ 3.60GHz
Memory: 31.1 GiB of RAM
Graphics Processor: NVIDIA GeForce GTX 1080 Ti/PCIe/SSE2

ADDITIONAL INFORMATION
Tablet: Wacom Intuos Draw Small -  CTH-490

Enabling touch mode on my tablet, so it functions as a touch screen, and then using my hand does work correctly. This issue seems specific to using the tablet pen.