Welcome to Microsoft Q&A, thank you for posting your question here!
To understand your question, you would like to use SharePoint as front-end and Azure Blob for storage.
As a longtime standing SharePoint Developer, in some years back this is not really available and about third-party software I will share some pre-shared on this platform in the past and for custom solution for those .js I do not know for now. But there are ways you can configure your SharePoint to use the Azure Blob direct or sync all your SharePoint files with Azure Blob.
- You can use Azure Blob Storage for SharePoint by creating a new storage account and a blob container in Azure portal.
- Then you can upload files in the container and create a new Azure Logic App to sync the blob files with a SharePoint document library.
- You can also copy documents from SharePoint Online to Azure Blob Storage using Power Automate.
To use Logic Apps
please refer to the following links on connecting logic apps with SharePoint as well as Azure Blob-
a. Connect to Azure Blob Storage - https://video2.skills-academy.com/en-us/azure/connectors/connectors-create-api-azureblobstorage?tabs=consumption
b. Connect to Share Point - https://video2.skills-academy.com/en-us/azure/connectors/connectors-create-api-sharepoint
Here is a similar thread- http://datanrg.blogspot.com/2021/05/a-blog-post-about-copying-azure-files.html
To Sync SharePoint Document Library with Azure Blob using Logic Apps. You can use this link:
Also, a similar answer in past is here for your review on Azure BLOB storage for SharePoint online.
To transfer or save Files from SharePoint to Blob Storage with Azure Logic Apps. You can read more from this link.
Now,
you can directly transfer from Azure blob to SP online using third-party tools that support these clouds and I would suggest trying Gs Richcopy 360 and Syncback Pro.
With any of these tools, you don't have to download from the blob and then upload to SP, both are created to do such a process easily and quickly.
Kindly let me know if the above helps or you need further clarification, assistance or more explanation on this issue.
Best Regards,
Sina