SUMMARY
When I open "System Settings/Text & Fonts/Fonts", choose a font and put any font features in the appropriate field, they don't get applied.

STEPS TO REPRODUCE
1. Open System Settings/Text & Fonts/Fonts
2. Set "Fixed width" font to Fira Code, with the font feature "ss05" (this displays a different style of the "@" symbol)
(2.5.) Type "@" in the sample field - the correct style of the symbol is displayed
3. Press "Apply"
(3.5.) Open the font selection window again - the "ss05" feature is still there
4. Close System Settings, then open System Settings/Text & Fonts/Fonts again
5. Open fixed width font selection - the "ss05" font feature is gone

OBSERVED RESULT
The "ss05" feature does not get preserved when System Settings are closed.

EXPECTED RESULT
"ss05" feature gets preserved.

SOFTWARE/OS VERSIONS
(available in the Info Center app, or by running `kinfo` in a terminal window)
Operating System: Kubuntu 25.10
KDE Plasma Version: 6.4.5
KDE Frameworks Version: 6.17.0
Qt Version: 6.9.2
Kernel Version: 6.17.0-8-generic (64-bit)
Graphics Platform: Wayland
Processors: 20 × 13th Gen Intel® Core™ i9-13900H
Memory: 16 GiB of RAM (15.2 GiB usable)
Graphics Processor: Intel® Iris® Xe Graphics

ADDITIONAL INFORMATION