Create an IAM policy that prohibits changes to the specific CloudTrail trail and apply the policy to the AWS account root user.

Create an S3 bucket policy in the specified destination account for the CloudTrail trail that prohibits configuration changes from the AWS account root user in the source account.

Create an SCP that prohibits changes to the specific CloudTrail trail and apply the SCP to the appropriate organizational unit or account in Organizations.

Create an IAM policy that prohibits changes to the specific CloudTrail trail and apply the policy to a new IAM group. Have team members use individual IAM accounts that are members of the new IAM group.