How to type Unicode characters in Linux?

Entering Unicode characters in any Linux application is easy if you know the exact, hexadecimal Unicode codepoint number (e.g. U+1F600):

  1. Press and hold the left Ctrl and Shift keys,
  2. type U,
  4. and finally release Ctrl and Shift.
Now the typed-in text (U1F600) should disappear, and be replaced by the actual Unicode character, e.g. 😀.
This method works in GTK- and Qt-applications (all of Gnome and KDE), but also in other popular applications like Google Chrome or Visual Studio Code.