Good day,

Could someone advise on this? For some reason firefox does not want to use the kde theming, menus, title bars, pop ups etc.

As per attached, that should state "Breeze" just like in arch and opensuse.

Re-installing does not help, I have the auto-system theme selected.

(!)Solution:

Settings > Application Style > GNOME/GTK Application Style

If you have installed Fedora KDE it should be set to breeze by default.

1. Change it to the "default" option and then apply.
2. Change it back to breeze then apply and you should be set.