Four days ago I upgraded my Ubuntu workstation from 18.04 to 22.04 via "do-release-upgrade". Since then, I've encountered the following situation twice.
I go to bed at night after working on the system. When I wake in the morning and resume working on the system, I find that all input for my session is in Japanese instead of English.
This input change affects all the apps I've tried (Chrome, LibreOffice, Terminal, Notepadqq) but it is limited to the user account that I was logged in with when I stopped working overnight; If I login as a different user, that account accepts US English input as expected.
My fix has been to reboot the system, at which point the affected user's input returns to normal. I haven't tried a simple logout/login to see whether that also works.
I'm completely confused by this, because I've never used Japanese input in my life. I'm not even sure how to switch between input languages...hence my reboot to fix it.
I have Audacious running, and there are songs in the list with Japanese characters, but the currently-selected song (according to Audacious's metadata display) contains only English characters (although it is by a Japanese band - Shonen Knife.) That's the only Japanese-language connection that I can think of which is active in the running system.
I checked the "Region & Language" in Ubuntu's "Settings" the first time this occurred and the language was set to "English (United States)".
Any thoughts on what's causing this and how to fix the problem so it doesn't recur? Or, at the very least, how to switch back to English as the input language without a reboot of the system when it does happen?