Are you using the Samsung Keyboard ?
If so then launch your Samsung Keyboard.
Press the 3 little dots on the right hand side just above the letters on your Keyboard.
The icon that has a microphone should be there for you to drag into the options bar.
If not then you could reset your Keyboard to default settings as a last resort.
If I can be of any further help then please don't hesitate. Take care. 😎
Daily Driver > Samsung Galaxy s²² Ultra 256Gb in Phantom Black.
The advice I offer is my own and does not represent Samsung’s position.
I'm here to help.