There is some issue with Breeze Dark and flatpak+GTK application, then i found the solution for it there is the i config for that respecting breeze dark for the GTK3/GTK4, and other version GTK as possible (especially respecting the window control on left, offcourse for me 😁).

Install Breeze dark

1. Install Dark Breeze on flatpak

   flatpak install flathub org.gtk.Gtk3theme.Breeze-Dark
   

2. set the teme to breeze dark

   flatpak override --user --env=GTK_THEME=Breeze-Dark
   

qt6ct

this make integration have better experience with non-flatpak but you can skip this installation

1. Installing qt6ct for better implementation

   # pacman -S qt6ct
   

2. Set environtment to qt6ct set the QT_QPA_PLATFORMTHEME on file /etc/environtment:

   QT_QPA_PLATFORMTHEME=qt6ct
   

3. setup the qt6ct open the qt6ct by on meta/super menu or terminal, type: qt6ct to run. settings on qt6ct like this or may you can costumize by yourself its ok!

Results

There is the results for what i mplementation, some app its still have a libadwaita, but some gtk3 had theme set for breeze and/or dark mode respect (than before had a light theme adwaita)