====== Setup Vietnamese Input with fcitx5 ======
     
     sudo apt install fcitx5 fcitx5-chinese-addons fcitx5-diagnose
     
Additionally install some CJK fonts

     sudo apt install fonts-noto-cjk fonts-noto-cjk-extra
     sudo apt install xfonts-way

then update the font cache with 
     
     sudo fc-cache -f -v

Add the following environment variables 

<code>
#~/.profile
export XMODIFIERS=@im=fcitx5
export GTK_IM_MODULE=fcitx5
export QT_IM_MODULE=fcitx5
</code>

Check the setup:

    fcitx5-diagnose
    
Change default input method from ibus to fcitx5:

     sudo apt install im-config 
     im-config -c 

This adds the following configuration in .inputrc r .xinputrc

     run_im fcitx5
     

Select input method:

     fcitx5-configtool
     
Open a GUI application, gvim for instance, and click Ctrl+Space (or use language switcher top right) to switch from English input to Vietnamese input.

Google search shows, to support Wayland composer, .config/environment.d/profile.conf needs to be updated with the following content

     XMODIFIERS=@im=fcitx5
     QT_IM_MODULE=fcitx5
     GTK_IM_MODULE=fcitx5