Stream on SharePoint is replacing Stream Classic. Rather than being a separate product with its own storage, video content can simply be stored within SharePoint and access controlled using standard SharePoint permissions and features.
The Stream on SharePoint portal will collate this content for individual users based on what they can access.
For key differences regarding the two products see Stream (on SharePoint) vs Stream (Classic) Guide – Microsoft Support
For further details on Stream SharePoint and Microsoft developments see Features in Microsoft Stream (on SharePoint) – Microsoft Stream | Microsoft Learn
For advice on using Stream on SharePoint see Learn more about Stream (on SharePoint) – Microsoft Support
The Stream tile within M365 will redirect to Stream on SharePoint. You will be able to change between both products until Stream Classic is retired. However you will no longer be able to upload content into Stream Classic.
For more information on the transition from Stream Classic to Stream on SharePoint