If for some reason you need a user that’s RDP’ed into a Server or Workstation to do a CTRL+ALT+DEL, here are two ways to accomplish that.
1. In RDP, the “CTRL” + “ALT” + “End” combonation
2. In RDP, right click Windows logo and click on “Run”
Type: osk and press “OK” (opens On Screen Keybord)
Press “Crtl” and “Alt” on the physical keyboard and then “Del” on the OSK keyboard