I honestly don't know if you can make it work with a client or server setting. I suggest you try mstsc.exe or RDCM from Microsoft (https://www.microsoft.com/en-us/download/details.aspx?id=44989) to see if there's a setting which could make this work.
I'm getting this error when trying to use a Remote Desktop Gateway:
Return Code (Disconnect Reason) = 50331653: This computer can't verify the identity of the RD Gateway
Looking on my gateway I do not have a cert currently configured for Remote Desktop Gateway, and I believe that's the problem. My question/problem is there a way to tell Royal or the Gateway to ignore the identity/cert issue and just move on? Or does there absolutely need to be a cert on the Remote Desktop Gateway service for this to work?