Remote Desktop (RDP)
Worked through on Windows Server 2012 (R1) VM, which is not part of the domain.
Add the Remote Session Host Role
As an admin users, open the Server Manager.
Go to Add Roles and Features.
Click through until you get to server roles. In particular, ignore the Remote Desktop Services installation option under Installation Type - it's not helpful.
Add the Remote Desktop Services role, then when you get to the details of the role features, select Remote Session Host
Add users you want to be able to RDP in
Open Computer Management, and from there Local Users and Groups. Add some users to the Remote Desktop Users group.
On Linux, I found that Remmina was able to connect to this configuration without any trouble.
I did have to accept a certificate.