v1.9.1 is a feature release:

• Schema Registry support for Avro Generic and Specific, Protocol Buffers and JSON Schema. (@rayokota, #776).

• Built-in support for Mac OSX M1 / arm64. (#818).

confluent-kafka-go is based on librdkafka v1.9.1, see the librdkafka release notes for a complete list of changes, enhancements, fixes and upgrade considerations.