If it is a BT Keyboard specifically designed for iOS devices, it won’t have one. If it is a computer keyboard being used with an iOS device, it may have one. The Apple BT Keyboard for Mac, which can be used with iOS devices as well, does have one.
I‘ve never seen a Zagg iOS specific BT Keyboard with an eject key, nor a Logitech iOS specific one for that matter. There would be no point obviously, since an iOS device would never have anything to eject. Often iOS keyboard will have iOS device specific keys in place of others - like my two Logitech iOS specific keyboards with keys to lock the screen and to close apps and return to the home screen.
Logitech puts a dedicated key to switch between onscreen and physical keyboard in the lower left. It has the keyboard symbol on it.