Fcitx5 app
Supported languages
English (with spellcheck)
Chinese (Pinyin, Shuangpin, Wubi, Cangjie and custom tables)
Vietnamese (Based on UniKey, supports Telex, VNI and VIQR)
Features
Virtual Keyboard (layout not customizable yet)
Expandable candidate view
Clipboard management (plain text only)
Theming (custom color scheme and background image)
Popup preview on key press
Long press popup keyboard for convenient symbol input
Symbol and Emoji picker