To some extent. While it's inspired by real elements of Ma Rainey's life and the music scene of that time, there's creative interpretation and dramatization involved.
It has elements of truth, but it's not a completely accurate retelling. The story takes liberties to make it more engaging and cinematic while still drawing from real-life influences.
Yes, it's based on real events and real people. It offers a fictionalized account of some aspects, but has roots in truth.