The repository to that titlebar is GitHub - kem-a/macos-titlebar: This project provides GTK3 and GTK4 CSS stylesheets that apply MacOS-style buttons over the current GTK theme without changing it. It is designed to work with any Gnome desktop environment, I have used that titlebar on fedora 41 (gnome 47) without any issues, when I upgraded to fedora 42 to benefit from the new integrated stuff, that issue appeared in all of my tabs when they are maximized, any fix? I tried to mess with the gtk.css but nothing changed
Maybe lack of gnome 48 support?
You could raise a issue against the code of github about this.