Hello,
Disclaimer: I have never done this for korean but I have done it for chinese (I am only able to type "sun" in chinese in order to verify it is functional) I would not bother with under-the-hood manipulations: install the task- korean and task-korean-desktop packages. this will take care of needed fonts, input methods and all. This will not convert the user environment to korean but instead bring him the possibility to display and type korean inside his english environment. Then your user will be able by himself to click on an applet or a menu option (both are present, I think) to set up how he wants to input korean. Feel free to disagree but I would advise you against installing Sid rather than Bullseye for a user who is asking you to setup his korean environment, though: if he is not able to do this, how could he administer his computer?
