I already knew that Ctrl+Shift+u would allow to type a character by giving its Unicode hexadecimal representation: an underlined u appears, you type the code and hit Enter.
For example, Ctrl+Shift+u; e; 9; Enter gives the character é.
Now I've just noticed that Ctrl+Shift+e lets an underline e appear, in a very similar manner, but I can't figure out what it does.
Does someone know? Thank you in advance.
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
Based on other answers here, I discovered that this keyboard shortcut defaults to Ctrl+. for anyone running Ubuntu with the KDE desktop environment.
Typing this shortcut displays the same "underlined e" character in a text box and doesn't seem to want to disappear unless I type some additional characters after it and hit Enter. Then it just leaves me with the additional characters I typed.
using the ibus-setup command, I was able to confirm that, on my system, this emoji entry shortcut was set to <Control>period which I found myself accidentally hitting occasionally. Changing it to Ctrl + Shift + e will likely make this a lot less likely for me to accidentally activate
