Install gkrellm-xkb by entering the following commands in the terminal:
sudo apt update sudo apt install gkrellm-xkb
Description:
Keyboard layout indicator plugin for GKrellM
This GKrellM plugin indicates active X keyboard layout with country flag, lists configured layouts, allows you to switch between them, and also indicates Caps lock and Num lock status.
Homepage: http://www.sweb.cz/tripie/gkrellm/xkb/
Version: 1.05-5
Section: universe/x11