Everything worked as planned, the host was flexible and helpful. The room is indeed small, but during most of the weekend the entire apartment is available for the guest. (Ask the host when the apartment is empty.) Ask the host about Covid rules (test, vaccination, mask) in advance. The location is nice, there are plenty of restaurants and grocery stores nearby, Prater park and amusement park are nearby, and the rest of Vienna city center can be reached by U-Bahn and S-Bahn (both less than 8 minutes of walking distance).