Kaki usually a little late to leaf out so it avoid some of the late frost. Giombo, Hachiya, and Hao River are the real good larger Kakis that can handle your Zone 7.
I am not sure about Hachiya. While it might be cold hardy in your area it’s quite late ripening so I doubt it can properly ripen in Austria. Tony (while in zone 5) has warmer summers and autumns so we cannot compare with him. I asked about it in a local nursery which is selling many persimmons and they did not know cause their Hachiyas are in greenhouse.
You should try Cliff England’s “Korea Kaki”, because it is pretty cold hardy for a pure Asian persimmon. From what I can tell in pictures, I believe it is pretty similar to Steiermark. “Korea” hasn’t even flowered for me yet, so I cannot comment on flavor…
Isn’t Saijo typically the variety that is dried in Japan? I haven’t gotten any yet, but my tree is vigorous and growing well here in zone 7 central VA.