In Azure Update Manager, the process has evolved, and runbook-based patching is no longer directly integrated as it was in Update Management. Instead, Azure Update Manager focuses on automating patch orchestration without relying on runbooks. However, if you still need to use runbooks for custom logic or specific workflows, you can create automation workflows separately and trigger them using other mechanisms, such as Azure Automation or Logic Apps, alongside Azure Update Manager's features.
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hth
Marcin