Does an Azure Plan support Azure Hybrid Benefit for existing Windows Server/SQL licenses?

Yes — Azure Hybrid Benefit, which lets you apply your existing on-premises Windows Server or SQL Server licenses (with Software Assurance) toward discounted Azure compute costs, works the same way under an Azure Plan as it does under a direct subscription. It's a feature of Azure itself, not tied to a specific billing/commerce model.

Your CSP partner can help confirm your existing licenses qualify and that the benefit is correctly applied to the relevant VMs or databases.