/usr/include/fcitx/module/ is in fcitx-libs-dev 1:4.2.9.1-6.
This file is owned by root:root, with mode 0o755.
..
/usr/include/fcitx/module/chttrans/
/usr/include/fcitx/module/chttrans/chttrans.h
/usr/include/fcitx/module/chttrans/fcitx-chttrans.h
/usr/include/fcitx/module/classicui/
/usr/include/fcitx/module/classicui/classicuiinterface.h
/usr/include/fcitx/module/classicui/fcitx-classicui.h
/usr/include/fcitx/module/clipboard/
/usr/include/fcitx/module/clipboard/clipboard.h
/usr/include/fcitx/module/clipboard/fcitx-clipboard.h
/usr/include/fcitx/module/dbus/
/usr/include/fcitx/module/dbus/dbusstuff.h
/usr/include/fcitx/module/dbus/fcitx-dbus.h
/usr/include/fcitx/module/freedesktop-notify/
/usr/include/fcitx/module/freedesktop-notify/fcitx-freedesktop-notify.h
/usr/include/fcitx/module/freedesktop-notify/freedesktop-notify.h
/usr/include/fcitx/module/ipc/
/usr/include/fcitx/module/ipc/ipc.h
/usr/include/fcitx/module/lua/
/usr/include/fcitx/module/lua/fcitx-lua.h
/usr/include/fcitx/module/lua/luamod.h
/usr/include/fcitx/module/notificationitem/
/usr/include/fcitx/module/notificationitem/fcitx-notificationitem.h
/usr/include/fcitx/module/notificationitem/notificationitem.h
/usr/include/fcitx/module/pinyin/
/usr/include/fcitx/module/pinyin-enhance/
/usr/include/fcitx/module/pinyin-enhance/fcitx-pinyin-enhance.h
/usr/include/fcitx/module/pinyin-enhance/pinyin-enhance.h
/usr/include/fcitx/module/pinyin/fcitx-pinyin.h
/usr/include/fcitx/module/pinyin/pydef.h
/usr/include/fcitx/module/punc/
/usr/include/fcitx/module/punc/fcitx-punc.h
/usr/include/fcitx/module/punc/punc.h
/usr/include/fcitx/module/quickphrase/
/usr/include/fcitx/module/quickphrase/fcitx-quickphrase.h
/usr/include/fcitx/module/quickphrase/quickphrase.h
/usr/include/fcitx/module/spell/
/usr/include/fcitx/module/spell/fcitx-spell.h
/usr/include/fcitx/module/spell/spell.h
/usr/include/fcitx/module/x11/
/usr/include/fcitx/module/x11/fcitx-x11.h
/usr/include/fcitx/module/x11/x11stuff.h
/usr/include/fcitx/module/xkb/
/usr/include/fcitx/module/xkb/fcitx-xkb.h
/usr/include/fcitx/module/xkb/xkb.h