Sci-fi novel from early '90s about man fleeing dystopian Earth where interracial marriage is mandatory in stolen starship. Finds blackhole the size of a galaxy.

[Donald]

I found this paperbook book in a supermarket sometime around 1993, but cannot remember the title or author. A man flees a totalitarian Earth where interracial marriage is mandatory in a stolen starship on an adventure of discovery, such as finding a blackhole the size of a galaxy. That's really all I remember about it.