How to connect to Oracle ubuntu instance using RDP protocol via Windows or Ubuntu

I want to run selenium on my ubuntu server (oraclecloud) on instance type VM.Standard.A1.Flex. I did try to install RDP and connect with RDP client but connection is failing.

I followed multiple blogs on internet to install and connect using RDP but it is not working. I am getting following error while I am tring to make a connection.

Image of the error

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