Front light controls for H2O?

I searched and a thread led me to https://github.com/koreader/koreader/issues/2270

That page and the thread say that the addon became part of the official koreader, but I'm lost.

On my H2O, tapping in the bottom left, or swiping on the left doesn't do anything. Could someone give me more info on getting this to work?

Thanks!