Install fookb-plainx by entering the following commands in the terminal:
sudo apt update sudo apt install fookb-plainx
Description:
Xkb state indicator -- plain X version (transitional package)
WindowMaker docked Xkb state indicator. Fookb can switch xkb groups and display a pixmap corresponding to the selected group. It also can execute a specified command upon the switch (for example, play sound). This is the plain X-compiled version. It can't do docking, and uses only X resources for configuration. . This is a transitional package. It can safely be removed.
Homepage: http://www.dockapps.net/fookb
Version: 4.0-1
Section: universe/x11