Some apps (mainly Firefox but has also happened in a few other programs) are using GNOME GTK theming and UI elements instead of Plasma theming/elements despite the fact I am using the KDE Plasma desktop. Plasma is installed with services.displayManager.sddm.enable = true; services.desktopManager.plasma6.enable = true;. I currently have Firefox installed using programs.firefox.enable = true; in my system configuration. Any ideas?
Did you ever use GNOME in the past?
Also firefox uses gtk + its own framework, how would kde theme it?
I have not used GNOME, other than perhaps that was what the installation media used.
Other distros I have used have functioned correctly, even if I have also had GNOME installed along side Plasma and still have had the theming work out correctly.