having the same issue as saibot CocoaMQTT is basically abandoned at this point. I am planning on switching to MQTT-NIO

I figured it out, solution below

In a brand new project it works fine. Which is why I suspect something is wrong with our build config. I am just not sure where to begin because the app does not even reach the app delegate.

my solution was to wrap a UITextView in UIViewRepresentable. You can implement the new sizeThatFits API in UIViewRepresentable to ensure that the view sizes itself to fit its UIView content. Edit: Also using a TextField with a vertical growing axis seems to work as well. But the return button seems to submit the text field rather than adding new lines like one would expect.