When you use log shipping together with Always On Availability Groups in Microsoft SQL Server 2016 and 2017, log shipping can't detect available replica and fails with the following error message:
The backup operation on database 'DatabaseName' was skipped because it is part of an availability group and not its preferred backup replica
This problem is fixed in the following cumulative updates for SQL Server:
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.
Learn about the terminology that Microsoft uses to describe software updates.