Created attachment 165615 [details]
crash caught in gdb

SUMMARY
Closing kontact crashes kontact.

STEPS TO REPRODUCE
1. Open Kontact
2. Close Kontact

OBSERVED RESULT
Segmentation fault

EXPECTED RESULT
Clean close

SOFTWARE/OS VERSIONS
Operating System: Arch Linux 
KDE Plasma Version: 5.93.0
KDE Frameworks Version: 5.249.0
Qt Version: 6.7.0
Kernel Version: 6.7.3-arch1-1 (64-bit)
Graphics Platform: Wayland
Processors: 16 × AMD Ryzen 7 2700X Eight-Core Processor
Memory: 31.3 GiB of RAM
Graphics Processor: AMD Radeon RX 6500 XT

ADDITIONAL INFORMATION
I also was able to reproduce this in a clean install of kde (virtualbox arch testing) after closing all the kontact windows. (main window plus account wizard).
For what it's worth, I recently had a similar crash at exit of one of my qt6 apps caused by not manually deleting a dock window before tearing down the window. It turns out depending on qt ownership for a sane delete chain doesn't work the same way it once did, especially when a subroutine (I think it was a function related to my list widget) derefences a pointer back to the main window during the destruction process. not sure if that'll help here though?