In the Azure DevOps Server with SQL Server Reporting service (SSRS) there is a way to get unplanned work item report as stated here.
How to simulate the same report in Azure DevOps Service? Is ready-made report possible or some workaround is involved to get this functionality in Azure DevOps Service?
It appears that Microsoft currently support SQL Server Reporting through TFS 2018, and will continue to support it in Azure DevOps Server 2019 and 2020.
Azure DevOps Server 2020 is the last version to support SQL Server Reporting.
Future versions will support only Analytics.
Check this roadmap. This plan allows customers time to convert their reports to Analytics.
But this exact report might not be available in Analytics as is.
For future reporting check this documentation on Analytics.