I'm growing Vietnamese Red. Have tried one fruit. Still too few and too early to say, but the taste was actually okay. The seeds; however, were very hard and difficult to chew. Maybe I picked it too early? Cannot see eating this fruit out of hand if this is actually how the seeds are in typical ripe fruit. Maybe okay for juicing.
I have 2 Desertyni grafts on the Vietnamese Red tree. They are growing okay. No flowers as of yet. Grafts are over a year old.
Also have a Desertyni potted plant. May do more grafts from it.
Also, Parfianka is growing in ground, a year or less.
I am doubtful Parfianka or Desertyni will flower and fruit, but trying anyway. Will graft Parfianka to Vietnamese Red to see if that helps.
Oh, I also have a giant Mediterranean plant grown from cutting. Going to graft from it as well, onto VR.
My guess is Desertyni and Parfianka may flower and fruit in your area. I would try them both.