Hi @ eg1995 ,
If you are concerned about downtime caused by the fact that Office 365 and Exchange servers are different organizations after removing HWC, I recommend that you could refer to the following migration order:
1. First, move all on-premises mailboxes and related information to the cloud.
2. Delete the hybrid configuration.
3. Migrate all users directly to another tenant with cross-tenant migration.
4. Rerun the hybrid deployment in the new tenant.
In addition, I found some similar cases performed by other users, I hope to give you some inspiration:
office365 - Migrate hybrid Office 365 to new tenant - Server Fault (Kindly note: Microsoft provides third-party contact information to help you find additional information about this topic. This contact information may change without notice. Microsoft does not guarantee the accuracy of third-party contact information.)
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