Microsoft have made various announcements about removing the last Exchange Server from your Exchange Organisation if you have migrated all mailboxes (and mail functions) to Office 365.
https://learn.microsoft.com/en-gb/Exchange/manage-hybrid-exchange-recipients-with-management-tools
This is in the context that you still have Active Directory and Azure AD Connect, with all user accounts still mastered in Active Directory.
On first glance this looked very promising. If you had one remaining Exchange 2019 server with the latest CU update, then you could plan to install the Exchange Management Tools onto a different server or workstation.
And then use powershell to keep using the required Exchange Management Shell (EMS) cmdlets to create a remote-mailbox in Office 365.
However, on further reading you are asked to retain the last Exchange 2019 server and not de-install the Exchange application. If you do remove it then this will cause the Exchange Schema updates to be removed from Active Directory, removing the ability to manage the mail attributes for users on the other server/workstation. You are advised by Microsoft that you can power off the last Exchange 2019 server if you wish – this is not recommended by this blog as is untidy and not best practice.
My conclusion is that it would be better to keep using your last Exchange 2019 server for managing email attributes for AD users. And wait for a future announcement from Microsoft how we can actually remove the last Exchange 2019 server!
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