Sougou Pinyin dictionary, dump from https://pinyin.sogou.com/dict.
Use it with fcitx5:
yay -S fcitx5-pinyin-sougou
Or, download the repository manually, then convert it by:
cat dict/*.txt > dict.txt
libime_pinyindict dict.txt sougou.dict
Then put sougou.dict at ~/.local/share/fcitx5/pinyin/dictionaries.