Authorization problem using OS Benchmark against OS Serverless

Versions (relevant - OpenSearch/Dashboard/Server OS/Browser):
OpenSearch Serverless (AWS)
OpenSearch Benchmark

Describe the issue:
So I’ve recently run Opensearch Benchmark against an AWS OpenSearch cluster which worked fine.
I’m trying to do the same against an Opensearch serverless collection but I have extreme difficulty getting authentication both from within AWS (EC2) and outside (to a public endpoint).

Have anyone here actually managed to run an Opensearch benchmark against opensearch serverless?

Thank you.


Relevant Logs or Screenshots: