
Hi @Daniel Chee ,
These three site collections you mentioned are generated by default.
- https://tenantname.sharepoint.com/portals/community
You might or might not see this site collection in the list. In case you do, this site collection is a dedicated space with the Community features enabled. - https://tenantname.sharepoint.com/portals/hub
The second site collection in the list is /portals/hub. This is a site collection that contains all the videos you would post to the Office 365 Video Portal.
Reference: https://sharepointmaven.com/site-collections-sharepoint/
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In addition, there is no official documentation that says there is a lower limit for Storage Quota. I tried to modify a site collection with Storage Quota of 10 GB without any problems. So no minimum quota size is required to support its functionality.
Reference: https://learn.microsoft.com/en-us/sharepoint/manage-site-collection-storage-limits?source=recommendations
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