

The first link did have different instructions, but it didn’t solve the problem.
I also tried replacing Fcitx with Ibus, the other major IMF that may have better Gnome support. But I have the same problem plus others: on some apps like Firefox, the popup appears in the top left corner instead of where I am typing.
Edit: It is better now, see post edit, but still issue with popup being white on white.
Switching to Default (non-dark) style in Gnome Settings > Appearance doesn’t change the popup.
Also changing the appearance settings like font-size in
ibus-setup
does not change anything, so I’m thinking the popup I see is actually not from ibus but from mozc. I think the mozc pop-up doesn’t support dark theme at all according to what I have read, so this is a dead end for now.When I use the env var to force the use of ibus, I get the white rectangles.
I guess my only option now is to find a way for the ibus popup to recognize the Japanese font…