Is Minstrel a proper noun

No, the noun minstrel is a common noun, a Word for any traveling performer.

A proper noun is the name of a person, place, thing, or a title; for example:

• "Minstrel in the Gallery" album by Jethro Tull
• "Minstrels", poem by William Wordsworth
• Minstrel Way, Dayton OH or Minstrel Avenue, Los Angeles CA
• Boston Minstrel Company, non-profit entertainment organization