I am writing a worker service in .NET Core 7 which retrieves OUs, Groups & Users from Active Directory. Is there any good package to use for retrieving the information from Active Directory?
As suggested in the comment, you'll want to look at these inbuilt framework packages:
System.DirectoryServices.AccountManagement
These are fully compatible with .NET Core, and you should be able to do almost anything pertaining to AD using just these packages.