Etrade can trade GXG but all orders must be called in.
"Thank you for your message regarding GXG exchange.
I checked with our trading desk and we do have access to the GXG exchange. We would have to place the trade through our trading desk and you would not be able to see the order online until it executes. We would specify a limit price and try to work that order on the GXG exchange. Once the shares are in the account please give us a call and we can go from there."
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