The former boss confirmed he will not have any role at Old Trafford next season at the end of last month.
He intended to move into an advisory role this summer when he joined United in November but he will now stick with Austria.
And Rangnick is already producing in his new role – beating World Cup finalists Croatia 3-0 in the Nations League.
Former West Ham ace Marko Arnautovic fired in to open to scoring and give his side a half-time lead before Michael Gregoritsch and Marcel Sabitzer added two in three minutes after the break.
Austria now sit top of Nations League Group A1 and many United fans noted the victory was yet another damning indictment of the Red Devils squad.
One fan said: “Ralf Rangnick uses Austria to beat world cup finalists, Croatia, by three goals to nil and I am supposed to believe that he is not a good manager.
“The problem were those pathetic snakes at Man United.
Another added: “Ralf Rangnick (the worst coach ever coached United) is balling with a dead Austria team.
“The moment you realise the problem is United. The better for you.”
A third wrote: “He was never the problem, to me he influenced the solution to Man United’s problem but he was doing way to much at a point so the Glazers saw him as a threat.
“Austria was world-class today with just a game to show for it under Ralf. Ralf Rangnick is the unsung hero.”
