The biggest issue so far with kubuntu is it suboptimal language support, at least compared to regular Ubuntu. Luckily, it's very easy to add full Ubuntu-like support for non English languages by doing a small gnome-detour.
In a Konsole, run the following commands:
$ sudo apt install language-selector-gnomeWith the gnome-language-selector you can now configure the additional languages you wish to use.
gnome-language-selector package afterwards. Kubuntu has also a command line alternative, but I didn't test it by myself:
sudo apt install $(check-language-support)One last issue I had is that the Konsole (actually Bash) language was somehow set to French. Apparently, Bash is confused when the LANGUAGE environment variable has multiple elements. Start the KDE "Language" application and make sure you have only one "Preferred Language" set.
LANGUAGE has only a single language: