Upvote:1
The zoomable map at https://www.viennaairportlines.at/en/stops shows LiechtensteinstraΓe and the airport bus stop, 3-4 blocks from the tram terminal at Schottentor. The "stop info" says
Vienna Airport Lines buses stop on LiechtensteinstraΓe (by the LiechtensteinstraΓe exit from Schottentor underground station, on the U2 line).
which suggests that there is a separate eastern exit from the U-Bahn station.
The map at https://www.wien.gv.at/stadtplan/en/grafik.aspx?lang=en&bookmark=jildRsI0NEZJg6NErTsURO5RphlRnKnmkev2pn4Mpr4C appears to show the route of the airport bus as a green line. It agrees with the above map about the location, but on the other hand shows U2 one street over from where it looks like it is on Google Maps (and the few street photos I can find), so caveat lector.
(I have no personal experience with this location, but it grew too long for a comment).