To allow cp-kafka-connect connectors, for example S3, to access localstack resources in the cluster,
use the following not well documented configs:
"store.url": "http://localstack:4566",
"s3.region": "localstackDefinedRegion",
"s3.bucket.name": "someBucketName",
"aws.access.key.id": "test",
"aws.secret.access.key": "test"
Added this also to the only post I found about this issue: confluentinc/kafka-connect-storage-cloud#372