Profile option on AmazonS3Client

Please refer to the documentation. You can specify a profile (either from the shared credentials file or from a custom file) by using the CredentialProfileStoreChain class and obtaining an AWSCredentials object:

var storeChain = new CredentialProfileStoreChain();
if (storeChain.TryGetAWSCredentials("some_profile", out var awsCredentials))
{
    // Use awsCredentials to create an Amazon S3 service client
    using var client = new AmazonS3Client(awsCredentials);
}