Hey dad2noah, it's not a wise guy answer.... but that option ("don't show again") does not exist on my S5 (T-mobile, US).
It's just a white message at the bottom of the screen, that shows up EVERY time I unplug the USB cable.
Can you share the brand and model number, or link to amazon for your keyboard?
I've been looking high and low for one, and haven't found any good solutions.
TIA!