Hi,
This feature looks good in terms of bringing related sites under one umbrella. But it opens many questions, many of the addressed on the top also clarification on below queries.
1. Are there any possibility to use MS graph for collecting the events in different type of sites?
2. What happen is a group site is expired?
3. Is HUB site again a site collection or is it only to join different site at single place?
4. If HUB site is a site collection, are there any option available to publish the content from Hub site to connected sites?
5. Can user join hub site directly? If Yes, then what all joined user can do in hub site and connected site?
6. How security and access handled in hub site? for example I have access to a publishing content which resides in a sub site but does not have access to any other content in the subsite and toplevel site. Once the site collection added to hub site can I see the content?
7. Will all user get added to Hub site when a site collection attached to Hub Site? or Do we need to grant additional permission to the Hub site?
8. How to detach a site from Hub site?
9. What happened to users permission if site is detached from Hub site?
10. Will this support SPFx web parts?