I'm jealous. None of my mulberries are ripe yet here in SoCal. Pakistan, Kokuso, Australian White and Shangri La have lots of immature fruit still. Black Persian and Black Beauty are leafing out, haven't even started.
I was going to get rid of the Black Beauty because, with the climate change, it wasn't getting enough chill hours to produce at all, but decided to move the potted one to the coldest part of the yard and give it another year. I may dig up one of my Black Persians, pot it and try that as well. They are planted on the south side of the house, get some radiant heat from the warm house in the winter. That's not helping with the chill factor. A different location might help.