Japanese keyboard permanently destroys virtual keyboard (solution included)
I'll be making 2 issues regarding the keyboard, because one has a solution I've found, and the other is not yet solved.
In this case, I have a solution to the problem.
Once you enable Japanese keyboard, and switch to Japanese once the keyboard is up, the keyboard will freeze, and will never show up ever again until you re-install the OS altogether.
However, I found the solution to this problem (I don't want to take all the credit for it, because someone else on the internet happened to have solved the problem in the same way as I found out later on).
Basically, the keyboard is looking for Anthy as soon as you switch from English to Japanese.
But Anthy isn't installed by default, so after installing the keyboard was working again.
Perhaps this can be prevented by prompting to auto-install Anthy once "Japanese" gets enabled in the settings, and it's not yet installed?
Because once the OS gets properly localized and ready for mainstream use, I'm pretty sure many Japanese people will happily give Plasma Mobile a try.
The blog post is written in Japanese, but provides good details on how this problem got found and solved, with screenshots, CLI output, and a meme, so maybe useful for the devs here?
https://technicalsuwako.jp/blog/plasma-mobile-japanese-keybod-active