Ghostty by default looks like a gnome app even outside of gnome, with a hamburger menu and complete disregard for the system theme.
Put the values below in the config file, which for me was in .config/ghostty/config ;
and then close every ghostty window and restart the application for the changes
to take effect.
window-theme = system
gtk-titlebar = false
gtk-wide-tabs = false
gtk-adwaita = false