The exhibition, one of the world's premier showcases of art and culture, opened to visitors on Saturday and run until November 22.
Conflict over the participation of Russia and Israel led the entire jury to resign, and the Golden Lion will also not be awarded - something that has never happened since the festival was first held in 1895.
Prizes will now be awarded at the end of the event, based not on jury decisions but on a public vote.
On Friday, some 2000 people protested against Israel's inclusion, pointing to conditions in the Gaza Strip.
Police pushed back the throng with batons and shields.
Italian media reported that 20 national pavilions remained closed, as staff refused to work in protest at Israeli participation.
Journalists and art critics had been given a pre-opening preview of the pavilions.
Death also casts a shadow over the 2026 Biennale.
In 2025, Koyo Kouoh, appointed artistic director for 2026, died of cancer at age 57.
And in February, German installation artist Henrike Naumann, whose work represents Germany, died at 41, also of cancer.
The German pavilion is going ahead based on her ideas and those of German-Vietnamese artist Sung Tieu.