@socphoenix @On RDP server and client is Microsoft built-in, but bound to license restrictions. In general, 2 concurrent rdp sessions on one machine are possible without a need to extend the standard Windows license / price. You can add and license the rdp services role / terminalserver role to a machine setup and have more flexibility: more users, more administration of user sessions.
If your target is a Windows machine, you need a user that is a member of the target machine's local rdp or local admin security group, either directly or via a domain security group, start a client software (below) depending on your machine's operating system, enter the target machine's address (ip or name) and user name and password, and have a desktop session on the target machine in a window to remote comtrol it. You might need a VPN or citrix connection to the target's domain and you might need to qualify a user domain of your login credentials, but that's it in general.
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@socphoenix @On If the machine you are working at is on
* Windows: You can use Windows built-in RDP client mstsc.exe. There are alternatives and wrappers. I found that using mstsc.exe through RDP+ (https://donkz.nl) is the most reliable, comfortable, and safely automatable solution.
* Linux: You need a client software. I use Remmina (often in your distribution's standard repository) for that purpose. I understand from FreeRDP's linked and the github pages that FreeRDP is a concurrent client. It's tagged »Android« too. I usually need to work on the target and wouldn't torture myself with a mini and touch screen for RDP, so I personally don't mind.
You always need to try which client software works best in your situation and setup. So testing if FreeRDP is a client, and if for your operating system, can be done on the run.
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