Pi3B+ was released in March 2018!
Disregard my post. i didn’t realize there was a new pi out and was referring to the pi i just received with the wrong name.
Feel free to check out the method I describe in “How-To Set Up and Upgrade Ubuntu MATE 16.04 on a Pi 2/3/3B+”. It will get you up and running 16.04 or 18.04 on a 3B+