An Azure service that is used to automate, configure, and install updates across hybrid environments.
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After deboarding, the old schedules should no longer run, but there is no guaranteed cleanup time for when they disappear from the old update management UI. They may remain visible as disabled Automation schedules or software update configs until the portal refreshes, the old solution is removed from view or you manually clean up the old artifacts.
And because you set schedule migration to false, those old schedules were not migrated to Azure Update Manager since it uses maintenance configs for recurring schedules so you should recreate or migrate the required schedules there before deboarding the old solution.
https://learn.microsoft.com/en-us/azure/update-manager/scheduled-patching
https://github.com/azureautomation/Deboard-from-Azure-Automation-Update-Management