Via the New York Times, here is an early prototype of the Harriet Tubman version of the $20 bill:
Apparently the Times has good sources within the Bureau of Engraving! They report that this design was completed back in 2016:
The development of the note did not stop there. A current employee of the bureau, who asked not to be named because of the sensitivity of the matter, personally viewed a metal engraving plate and a digital image of a Tubman $20 bill while it was being reviewed by engravers and Secret Service officials as recently as May 2018. This person said that the design appeared to be far along in the process.
It’s worth noting that the Tubman bill was never intended to go into circulation anytime soon. Probably not until 2030, or the late 2020s at best. When Treasury Secretary Steve Mnuchin delayed the bill, the only thing he delayed was the unveiling of the design next year, in time for the 100th anniversary of the 19th Amendment. He was apparently afraid that a mere public unveiling of the bill would send Donald Trump into a tizzy that might embarrass everyone. It’s like having a five-year-old for president.