xfce – mozc seems to be nonfunctional, no Japanese characters appear

I am using Ubuntu 23.04 lunar with Xfce.

I want to be able to type in Japanese language.

I installed iBus and mozc.

It does not seem to be functional. I do see “Japanese – Mozc” in the IBus Preferences as a possible Input Method, and I can switch to mozc using Shift-Super-Space (a pop-up appears) but it seems to be totally non-functional. I.e. wherever I type, I just see latin characters. It does not convert or display to Kana, it does not suggest Kanji. It is just like typing on an ordinary US keyboard.