Install uim-gtk3 by entering the following commands in the terminal:
sudo apt update sudo apt install uim-gtk3
Description:
Universal Input Method - GTK+3.x front end
Uim is an input method module library which supports various scripts and can act as a front end for a range of input methods, including Anthy, Canna, or SKK (for Japanese), Pinyin (for Chinese), Byeoru (for Korean), and M17n (for many other languages). Most of its functions are implemented in Scheme, so it's very simple and flexible. . This package contains an GTK+3.0 front-end applications for uim.
Homepage: https://github.com/uim/uim/wiki
Version: 1:1.8.6+gh20180114.64e3173-2build2
Section: universe/x11