For me, Heliboard is the best option. FlorisBoard is cool too if you like their interface, but Heliboard is super customisable. You can change the symbols around, padding, colours, etc., and it supports plenty of languages and can work well with Whisper for TTS, and the auto complete suggestions is quite accurate in my experience. You can also change the toolbar to include copy paste, undo and redo, left/right, etc.