/opt/deepinwine/apps/Deepin-WeChat/run.sh 文件开头添加如下代码即可解决

export GTK_IM_MODULE=fcitx
export QT_IM_MODULE=fcitx
export XMODIFIERS="@im=fcitx"

最终代码如下

#!/bin/sh

#   Copyright (C) 2016 Deepin, Inc.
#
#   Author:     Li LongYu <lilongyu@linuxdeepin.com>
#               Peng Hao <penghao@linuxdeepin.com>

export GTK_IM_MODULE=fcitx
export QT_IM_MODULE=fcitx
export XMODIFIERS="@im=fcitx"

BOTTLENAME="Deepin-WeChat"
APPVER="2.6.8.65deepin0"
EXEC_PATH="c:/Program Files/Tencent/WeChat/WeChat.exe"

if [ -n "$EXEC_PATH" ];then
    /opt/deepinwine/tools/run_v2.sh $BOTTLENAME $APPVER "$EXEC_PATH" "$@"
else
    /opt/deepinwine/tools/run_v2.sh $BOTTLENAME $APPVER "uninstaller.exe" "$@"
fi