Until the most recent updates I could use my iPad Pro Smart Keyboard Folio to chat. Hearthstone client versions that I have confirmed not to work:

15.6.36453

16.0.37060

16.0.38203

The folio keyboard still works in the collection manager but does not work when trying to send chat messages. The iPad reacts correctly in that the interface reflects that its ready for keyboard input, but any input from the keyboard is not reflected in the client.

iPad Specs: