With the Server Core option chosen during the installation of Windows Server, I've seen several references to no GUI being present. I'm totally blind and as a result screenshots arn't that useful to me, but just so that I can get an understanding of how this works, when a user logs into a machine with Server Core what do you see? Is there still a Start button, or is the screen blank?
No GUI shell, there is only the console.
LoginUI.exe is text based. Then you are dropped into a cmd.exe. Do everything at a PowerShell prompt. There is window management, but no Start menu and no desktop, only a blank black screen. Task Manager is still useful for running new shells and reviewing processes.
I am not qualified to say how good screen readers are in this environment.
Remote management from a desktop is a better experience for everybody. Possibly even more so if you can access full ease of access tools.
If you use remote desktop it is really close to a basic xserver session with an xterm (if you know linux). With remote desktop you see a black background and 1 or 2 cmd windows (it depends on the win server version). If 2, the second one runs an helper script named sconfig and used to speed up standard activities: set an IP, check updates... Still you can download and install and use gui tools like firefox.
Entering via powershell it is like any other windows where powershell Enter-PSsession is enabled: just your ps window (a la ssh if you know linux)