Created attachment 151972 [details]
Screencap of KDE File Chooser from XDG portal for Brave as it is at the time of the report

SUMMARY

The file picker utilized by certain GTK programs from XDG Desktop Portal like Firefox, Chromium, etc. Now uses this default "Breeze" color scheme with a different button theme. I think this file picker now uses Qt6 but I'm not too sure. This breaks the consistency of the desktop theme on KDE Plasma.

STEPS TO REPRODUCE
1. Open a GTK-based web browser using xdg-desktop-portal-kde (Firefox, Chromium, Brave, etc.)
2. Right click on a web page and click "Save as..."

OBSERVED RESULT
KDE's file chooser uses the default color scheme with a different looking button theme

EXPECTED RESULT
KDE's file chooser should match color and theme set by KDE's System Settings

SOFTWARE/OS VERSIONS
OS: Arch Linux
Kernel Version: 5.19.7
KDE Plasma Version: 5.25.5
KDE Frameworks Version: 5.97.0
Qt Version: 5.15.6

ADDITIONAL INFORMATION
KDE's file chooser for KDE applications (Kdenlive, Kate, etc.) and Qt applications (LibreOffice, Clementine, etc.) are not affected by this bug. They look the way they should hence why this bug is being reported on xdg-desktop-portal-kde.