Windows Server 2016 ADFS - Integration with AWS Directory Service

We would like to use WebSSO(single sign on with a single set of credentials) for a number of small in-house web applications using Windows Server 2016 - ADFS (active directory federation service) and AWS Directory Service. We had created a domain using Directory Service in our AWS Account. I tried installing and configuring ADFS using Server Manager Tool on a Windows Server 2016 EC2 Instance after performing a successful domain join to the AWS Directory Service. One of the screens in ADFS Configuration Wizard is asking for a Domain Administrator password. The admin user created by AWS Directory Service does not appear to be a domain administrator. So I could not configure ADFS on the Windows EC2 Instance.

I was wondering if it is possible at all to create a Domain Administrator in AWS Directory Service and secondly is it possible to implement ADFS with AWS Directory Service using SAML?

From the below AWS link, I think the default "admin" user is not the same as a domain administrator.

Any inputs on ADFS integration with AWS Directory Service for web applications will be gratefully received.

Note: I found links on the net to install/configure Windows ADFS with Windows Active directory but not with AWS Directory Service. I found the below link for integrating ADFS with Active directory for IAM users, but did not help us much.

We are interested to integrate our web applications with ADFS/AWS Directory Service for WebSSO.