Install gtk3-nocsd by entering the following commands in the terminal:
sudo apt update sudo apt install gtk3-nocsd
Description:
Disable Gtk+ 3 client side decorations (CSD)
gtk3-nocsd LD_PRELOADs a small library to disable the client side decorations (CSD) of Gtk+ 3. . Since Gtk+ 3.10, its developers added a so-called header bar or custom title bar. With this and the client-side decoration, the original title bar and window border provided by the window manager are disabled by Gtk+. This makes all Gtk+ 3 programs look like alike, but have different handling from other windows on non-GNOME desktops. Even worse, this may break some window manager or compositors. . Unfortunately, there is no reliable way of turning off CSDs in Gtk+ directly. This library makes this possible.
Homepage: https://github.com/PCMan/gtk3-nocsd
Version: 3-1ubuntu1
Section: universe/x11