It is true that Vivaldi can be legitimately played in A440. That was his pitch in Venice.
But most amateurs I’m aware of, who are serious about baroque performance, will generally do so in A415. Many pros do perform or cut CDs at A415 and a few are exploring various original pitches (A403-410, A398-A400, etc).
All very exciting!
Mainly French & English baroque repertoire on an A403 Bressan, and an A415 DeBey. Recorder enthusiast since 1971. Early Music program at York University, French baroque instruction at Royal Conservatory in Toronto.