When you press [T] or / the chat opens corectly but you wont be able to type unless you press either [Backspace] or click on the chat box. Ssame goes for phones I think; if you open the chat, the keyboard won't pop-up unless you tap on the chat box. That's should be fixed as you cant chat at the correct time if you are not used to the bug and be confused. A whole text might be wasted bec the chat box hasn't been updated by the opening of the chat menu.
Thank you for your report!
We're actually already tracking this issue at MCPE-56228, so I will resolve and link this ticket as a duplicate.
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