Created attachment 167104 [details]
kde settings showing gtk theme is empty unset

SUMMARY:
kde-gtk-config does not default on breeze and creates empty strings for gtk-theme inside gtk config files it creates.
Tested this on archlinux without any customizations. 
(see picture 1 in attachment)

Strange thing is that if i install the complete kde-applications group it does work to use breeze by default without the need to set this manually. 

But installing kde-gtk-config itself seems to miss a dependency, could be archlinux packaging issue too... but i do not see missing dependency from what i checked on the source of it. And i checked https://community.kde.org/Distributions/Packaging_Recommendations  to have all needed packages installed. 

Question is may more general about what exactly is needed to set default in GTK theme settings?

STEPS TO REPRODUCE
1. install archlinux excluded kde-applications group (using default theme (Breeze) no changes), breeze-gtk and kde-gtk-config installed. 
2. check settings for GTK theme and see it is unset.
    possible to set it to breeze and it does apply too but sahould be set to breeze by default.
3. installing complete kde-applications group remove all gtk configs in home relogin and see it sets breeze as default selected gtk thme in settings. 

OBSERVED RESULT
Check settings for GTK theme and see it is unset (empty see picture 2 in attachment)

EXPECTED RESULT
If Breeze is installed and kde-gtk-config plus breeze-gtk it should set breeze by default for gtk applications in kde settings.

SOFTWARE/OS VERSIONS
Linux/KDE Plasma: 
linux 6.7.9.arch1-1 // plasma 6.0.1-1
KDE Plasma Version: 6.0.1-1
KDE Frameworks Version: 6.0.1-1
Qt Version: 6.6.2-4