Dussolier is seen having sex with a man and a woman in episode 6 of season 1.
Assente confirms his homosexuality in private conversation with Pope Pius XIII in episode 2 of season 1.
Though Izzy never actually states her sexual identity, it is assumed that she is likely Bisexual or Pansexual.
Emma is Bisexual and admitted to having a few romantic and sexual relationships with women in the past.
During a flashback, it is confirmed that Katherine is queer, and that she dated a friend from college before her death in a car accident that Katherine survived (another character references the girl as "the love of her life").