Actually, I do. Or at least I do in very similar situations where for some reason there is no keyboard shortcut to submit from the input field, so I press Tab (which moves the keyboard focus to the submit button next to the text field) and then press Return or Space to press the UI button.
Regarding on mobile, I’m familiar with chat apps that require a UI button press to send, and consider it unnecessary friction. It’s a larger mental leap to have to leave the keyboard.