MediaWiki Stakeholders have been working on a new LDAP stack to connect MediaWiki with LDAP based user directories. We have made considerable progress over the last months and the stack has been tested successfully in various contexts. The new stack is meant to replace the existing Extension:Ldap_Authentication which is no longer maintained. It integrates with AuthManager and is built in a modular and extensible way. There is also a documentation on MediaWiki.org  for how to use the new stack and how to migrate from the old extension.
In order to harden the stack against a range of use cases, we appreciate your testing and feedback. You can also contribute to the code directly, of course.
MediaWiki Stakeholders' Group