Hi @Vandmand, thanks for reporting. The font Noto Sans CJK KR (available on the Web Fonts list) supports korean characters. If you copy a text in koren from somewhere and paste it in Gravit, the font will be changed automatically to Noto Sans CJK KR.
About the bug you mention, just to clarify: you are using a non-latin keyboard and typing with a not-korean font (like Open Sans for examle)? Is it possible to record a video of this issue?