Fcitx5 Not Working on Plasma While Chromium Works

TuskedEvening0

TLDR:
Arch Linux 20240802. Plasma Wayland. Using Arch source's Chromium & Vivaldi and both enabled Wayland and "--enable-wayland-ime". Fcitx5 works on Chromium but not Vivaldi.

I recently encounter a problem that Fcitx5 does not work on Vivaldi, but other programs works, so I tried to find the reason. I tried to force it to use X11 but did not work, then I thought that it may be Chromium-based browser's fault, so I made a not-so-strict controlled experiment.

Chromium's argument:

%U --enable-features=UseOzonePlatform --enable-wayland-ime

Vivaldi's argument:

%U --enable-wayland-ime --enable-features=UseOzonePlatform

/etc/environment

user@TUSKEDEV ~> cat /etc/environment 
#
# This file is parsed by pam_env module
#
# Syntax: simple "KEY=VAL" pairs on separate lines
#

#GTK_IM_MODULE=fcitx
#QT_IM_MODULE=fcitx
XMODIFIERS=@im=fcitx
#SDL_IM_MODULE=fcitx
GLFW_IM_MODULE=ibus

fastfetch

user@TUSKEDEV ~> fastfetch
                  -`                     user@TUSKEDEV
                 .o+`                    -------------
                `ooo/                    OS: Arch Linux x86_64
               `+oooo:                   Host: 21D1 (ThinkBook 16 G4+ ARA)
              `+oooooo:                  Kernel: Linux 6.10.2-arch1-1
              -+oooooo+:                 Uptime: 2 days, 1 hour, 48 mins
            `/:-:++oooo+:                Packages: 1587 (pacman)
           `/++++/+++++++:               Shell: fish 3.7.1
          `/++++++++++++++:              Display (CSO1615): 2560x1600 @ 60 Hz (as 2048x1280) in 16″ [Built-in]
         `/+++ooooooooooooo/`            DE: KDE Plasma 6.1.3
        ./ooosssso++osssssso+`           WM: KWin (Wayland)
       .oossssso-````/ossssss+`          WM Theme: Breeze 微风
      -osssssso.      :ssssssso.         Theme: Breeze (Dark) [Qt], Breeze-Dark [GTK2], Breeze [GTK3]
     :osssssss/        osssso+++.        Icons: breeze-dark [Qt], breeze-dark [GTK2/3/4]
    /ossssssss/        +ssssooo/-        Font: Noto Sans CJK SC (10pt) [Qt], Noto Sans CJK SC (10pt) [GTK2/3/4]
  `/ossssso+/:-        -:/+osssso+-      Cursor: breeze (24px)
 `+sso+:-`                 `.-/+oso:     Terminal: konsole 24.5.2
`++:.                           `-/+/    CPU: AMD Ryzen 7 6800H (16) @ 4.79 GHz
.`                                 `/    GPU: AMD Radeon 680M [Integrated]
                                         Memory: 9.98 GiB / 27.10 GiB (37%)
                                         Swap: 18.75 MiB / 42.15 GiB (0%)
                                         Disk (/): 220.27 GiB / 436.88 GiB (50%) - btrfs
                                         Local IP (wlan0): 192.168.31.200/24
                                         Battery: 98% [AC Connected]
                                         Locale: zh_CN.UTF-8

~~No uploaded screen record.~~
On Chromium, Fcitx5 can change input methods and input to the website input box, but on Vivaldi, it is just simply not responding, with no ime changing and nothing output.
On other programs, it works well and smoothly, so that cannot be Fcitx5's problem.
By the way, which logs are needed to diagnose? Is it really a bug which is needed to report?

By the way, before switching from GNOME to Plasma, Fcitx5 works on Vivaldi X11, but not on Vivaldi Wayland. I tried "--enable-features=UseOzonePlatform --ozone-platform=wayland --gtk-version=4" and other 2 options provided by Fcitx5 Wiki, and Fcitx5 on Vivaldi Wayland was still not working. Due to the change and the lost of almost everything on my computer, I now have no log related to it, so won't report.

vishv

Same problem here. However, fcitx5 works with vivaldi-flatpak (but some extensions which want to see local files like video Download helper then fail.)

How to get someone to solve this (reported a bug)?