Dando uma pesquisada eu achei um comando com essa funcionalidade: Hit Control + Shift + E depois aperte Space.

Achei isso nesse link: https://askubuntu.com/questions/1045915/how-to-insert-an-emoji-into-a-text-in-ubuntu-18-04-and-later#:~:text=Use%20the%20following%20keyboard%20shortcuts,can%20select%20your%20unicode%20character.