Flatpak Theming / Fedora Kinoite

Hello all,

I have installed fedora kinoite and everything is working as expected, except theming.

I know this is a limitation due to sandboxing and that there is a way around it.

Now, all guides are either only for Gnome theming or 2-4 years old.

Is there a simplified way on how to make applications like Firefox and libreoffice use the standard breeze dark KDE theme?