Just who knew Arturia was female when she was King? Originally, I thought Merlin, Lancelot, Guinevere, Morgan le Fay and Mordred were the only people who knew Arturia was female when she was king. 

While reading up on Kay's profile on the Wikia, I read that he knew she was a female and vowed to keep it a secret


  Her identity as being female was known to him, but he kept the secret all his life after being sworn to secrecy by Merlin.


So this got me wondering: Was there anyone else who knew that King Arturia was in fact a woman? How did they find out?
According to Garden of Avalon, only Merlin, Uther (before he died), Ector (her foster father that raised her from the age of 5), Kay (her foster brother), and Guinevere once they married. Closer to the end of Artoria's kingdom, Guinevere reveals this to Lancelot as well once they start getting closer.

In the Camelot chapter in Fate/Grand Order, Agravain reveals that he found out about it when he discovered the affair.

While not explicitly stated anywhere I'm aware of, the circumstances of Mordred's conception/raising imply Morgan must have known as well.