SUMMARY
Normally draggable elements do not respond to drags made with a tablet pen. 
This includes emails in the message list, and folders in the sidebar.

STEPS TO REPRODUCE
1. Use a tablet pen
2. Attempt to drag an email from the message list into a different folder

OBSERVED RESULT
The email is not dragged, and only registers the initial click

EXPECTED RESULT
The email is dragged as when using a mouse

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
KMail: 6.1.0 (24.05.0)

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