PopOS/Ubuntu fcitx-rime setup
By my recommendation, my new workmate He (贺) moved to Ubuntu from windows, and he was annoyed of one thing: cannot input Chinese. And I have to google again to find out the answer. This is why I wrote this list for him like people and myself.
sudo apt install fcitx fcitx-rime
im-config # and select fcitx as the input engine
fcitx-configtool # > Add input method, remember to tick off `Only Show Current Language`