As to OP’s question, here’s a photo of my ’84 Five Star in the sloping top-tube variant:
https://www.bikeforums.net/21161437-post10.html
It’s a single sloping top tube that ends at the seatpost, but two thinner stay tubes continue on to the rear drop-out— not sure if that technically allows it to be called a mixte.
Edit: @
Bogester— now’s your chance to add Five Star to your list!