Created attachment 143875 [details]
Backtrace report autocreated by kcrash and edited by user for completeness

Discover crashes upon start with segmentation fault. It seems to be related to the Flatpak-backend. When uninstalling Flatpak-backend, Discover starts normal.
Backtrace - with hopefully all required debug symbols - provided in attachment.

STEPS TO REPRODUCE
1.  Install flatpak backend
2.  Start Discover

OBSERVED RESULT
Discover crashes with seg. fault

EXPECTED RESULT
Discover should run

SOFTWARE/OS VERSIONS
Windows: n/a
macOS: n/a
Linux/KDE Plasma: 
(available in About System)
KDE Plasma Version: 5.23.3
KDE Frameworks Version:  5.88.0
Qt Version:  5.15.3

ADDITIONAL INFORMATION
Other information that may or may not be useful:
System (KDE-Neon) is up to date (through pkcon) as per Nov 23, 2021 16:00;
The crash can be reproduced every time, but only on this system;
All installed flatpaks are SYSTEM installations (i.e. not USER);
Previously there was a flatpak test built of the Kvantum Qt engine installed (cant remember whether as system or user installation). Since the Kvantum flatpak has been merged to release (org.kde.KStyle.Kvantum) I have removed the test built, substituted it with org.kde.KStyle.Kvantum. I am not sure, but the Discover crashes may have started around that time I removed that test built from flatpak.