I work under ROSA Fresh R8 with Plasma 5, and I just have a problem with "system settings" in "Applications appearance" and "Gnome Apps Style".
I can't change the gtk3 theme and get stuck to Breeze theme. When I try to apply this setting change, I get an error window. See picture link below (In english: "unable to save settings").
I would like to try to edit manually the configuration file but don't know where it is stored.
Thanks for reading and helping.