I have a Late 2012 Mac Mini on Mojave. I have Screen Sharing activated and can connect remotely to the computer using the facility in Jamf Remote. I see the login screen but it does not respond to either mouse or keyboard input. I'm not in observer mode on the client. Firewall is off. I've tried disabling and re-enabling Screen Sharing without success, and I don't have issues on any other machine in my environment running the latest revision of Mojave.