ctrl+shift+e causes beeping

Seee https://askubuntu.com/a/1039039

One needs to run ibus-setup and in the tab "Emoji" change the shortcut (click on the three dots that are focused in the screenshot)

According to this page (archive), CtrlShifte is a key-combination offered by Gnome's input method to input an Emoji. It is similar to CtrlShiftu that allows you to enter an arbitrary character by specifying its Unicode number. Here, instead of a number, you specify an Emoji name, like "kiss", "grin" or "<3".