Does anyone know if the yellow tourist tram closed permanently? I looked online and it says closed, but not sure for how long.
It has not been operating since COVID started. To be honest, you can see exactly the same stuff with the normal tram. Or you can walk counterclockwise from Votivkirche, past the Rathaus, Burgtheater, Volksgarten, Parliament, KHM, Hofburg and stop at the Opera - you will have seen the highlights.
Wiener Linien, Vienna's public transport operator, does not provide a date yet for the re-opening of the Vienna Ring Tram.
But you can check here from time to time:
https://www.viennasightseeing.at/vienna-ring-tram