Design question for a hub-spoke models

We have a clients that has done a series M&A in the past couple years. Each Acquired company has different user foot print varied from a couple hundreds up to a thousand. One company purchased Okta last year and head office plans to role to rest of companies - operational wise they are separate entity each has own AD and maintains its own identity life cycle. Is there a good design pattern or best practise that you can point me into.

If you have not already had the opportunity to review it I would suggest the following resource,

Erik, thanks for the quick reply. Will review the link.