In my past blog, I wrote about how to set up i3 Japanese input environment .
This time I wrote about how to set up Czech input environment on i3. The articles ,  were helpful.
First check the current keyword setting by
$ setxkbmap -query rules: evdev model: pc105 layout: us,cz variant: ,
Then here is the setting to change the keyboard by toggle, typing Shift + Alt. I confirmed it works on the terminal.
$ setxkbmap -layout us,cz -option grp:alt_shift_toggle
Here is the setting typing Alt + Space. This one is my favorite setting. But as it does not work on VIM, maybe because space is occupied by another setting of mine. I did not set this one.
$ setxkbmap -layout us,cz -option grp:alt_space_toggle
Then add the following config to the config file.
$ vi ~/.config/i3/config ... exec --no-startup-id "setxkbmap -layout us,cz -option grp:alt_shift_toggle" ...
Load the setting by typing Window key + Shift + r.
Now the updated setting is like this.
$ setxkbmap -query rules: evdev model: pc105 layout: us,cz variant: , options: grp:alt_shift_toggle
-  http://junaruga.hatenablog.com/entry/2020/09/21/054421
-  ttps://www.reddit.com/r/i3wm/comments/jxrloz/change_input_language/
-  https://faq.i3wm.org/question/4761/keyboard-input-language-problems-want-to-switch-to-greek/index.html