From the Juno, elementary support iBus as a default input-method-framework. Thus, someone who want to type in Hangul(Korean Alphabet) in Juno and using Korean locale(Asia/Seoul with Korean 101/104 keyboard layout). You should use ibus-hangul which would be installed while installing Juno. In that case, you shoud do this after the installation.
* system settings - keyboard - Input Method settings * delete english keyboard layout (since the bug of ibus)
And you need to know as well, there might be an issue with inputting Hangul in some online service and apps like Facebook, and some development tools while using ibus-hangul. I would recommend to you to use nimf as your Hangul input method for Korean.
sudo apt install software-properties-common sudo apt-add-repository ppa:hodong/nimf sudo apt update sudo apt install nimf nimf-libhangul im-config -n nimf Logout & Login nimf-settings
But, If you are in other locale , it might not be installed by default. In that case, you should install ibus-hangul manually.
sudo apt install ibus-hangul im-config -n ibus-hangul logout & login
or it might be better to use nimf as your input method like Korean.
elementary OS team needed to implement input method for universial users, so they load iBus as a default input-method-framework for those universial users like Korean, Japanese, Chinese and more...
This guide is for the people who want to input Hangul(Korean Alphabet) but might help for other input methods user as well, I hope so.
Thank you for reading it.