The T9 for Dutch is missing a lot of very simple and common words, like the whole "to be" verb. switching from and to T9 takes more time than simply spelling out each word. rendering T9 useless right now.
It would be nice if we can add words as well. :)
I'm on KaiOS version 12
Experiencing the same issue re Dutch language - reported a bug to KaiOS so hopefully it will be fixed.
The text prediction in general is the worst thing about this phone at the moment - it really needs the ability to add words to a custom user dictionary.