Hello friends, I am using PRO 6, and here snapchat has the same annoying black bar.
I found a way to remove it, but need to do every time you will take a photo.
First open snapchat, then go to messege menu.
Second, pretend that you are going to send a text message to anyone and type something on keyboard, just to open the keyboard.
Third, once you opened the keyboard on messege board, the black bar will be gone at this session with snapchat open.

I don't use messengers, they take too much time.

nooooooooooooooo