I was looking into installing Sitecore 9.1 and was reviewing the modules compatibility table for XP (https://kb.sitecore.net/articles/541788) and was surprised to see no support for Active Directory modules. That would be a deal breaker for us. Did they replace it with something else to allow you to configure connectivity with Active Directory? Please and thank you.
Sitecore 9.1 uses an Identity server to handle logins instead of the old methods.
"With federated authentication now in widespread use across the industry, Sitecore finally provides user authentication and authorization through a centralized federation service. Built and run as a separate application, Identity replaces the traditional Sitecore login process, and provides federated authentication options and single-sign services in one portal."
9.1 sitecore updates
Sitecore 9.1 Identity Server