Thanks! Yes thought of XUL but didnt remember the name. It inherits lots of style from GTK but is not GTK. Actually I really like the Firefox toolkit, it is so damn beatiful.
I hate using Chromium, its just worse.
I will switch from Fedora Kinoite to Kinoite-hardened-laptop from Secureblue, which removes Firefox, but I am currently writing a small script to make the transition to using the standalone Tar archive easier.