So, on a vm that has polkit
Open two ssh sessions
Session one, echo $$ to get the pid of your shell
Session two, pkttyagent --process <pid>
Session one, visudo /etc/sudoers.d/rsync
or what ever other command you want as root
Session two, authenticate as the user
You will notice the prompt is the same as the one when you try start/stop/restart/reload a systemd service