What does [Ctrl] + [Shift] + [e] do, while typing text?

Ctrl+Shift+e is the emoji entry shortcut/hotkey sequence.

It produces an underlined "e̲", if you type "joy" after it (so it looks like "e̲j̲o̲y̲") the whole word will be underlined. On pressing a whitespace entry key, like spacebar, you should then get the "e̲j̲o̲y̲" text changed to "" (the emoji character selected by your current application).

Just issue the command bellow:

ibus-setup

And change it on the Emoji tab as the picture bellow