I had some difficulty trying to sort out multilingual spell checking with Sonnet. Eventually I found out that the process appears to be: KDE Plasma system settings → regional settings → language and add the desired language. Next, install the desired hunspell dictionary in Discover (the software center). The process appears to work properly, but my secondary language has now taken over the terminal, while the remainder of the system is in English, as it all should be. At this point this post is mainly a sanity check to hear if I am correct in my assumption that this is a bug, or if I have done something wrong…