Migration of SharePoint data from one SharePoint tenant to another is essential when there is a merger or acquisition between two organizations. Many Office 365 administrators find that the migration of Exchange data relatively easy as compared to the migration of SharePoint data. This is because of the complexity of SharePoint environment and absence of simple native methods for the migration of data from one SharePoint Server to another. Also, SharePoint tenant to tenant migration helps organizations to consolidate their SharePoint Online assets.
Because of the unavailability of a secure manual migration method, you can go for the automated process using migration tool. It is the most direct migration tool that can complete a secure SharePoint tenant to tenant migration without any issue. Here, we will go through the whole process of adding a SharePoint site as the source and another as the destination for copying the data between them.
Kernel Migrator for SharePoint
The tool uses a simple graphical user interface for the whole process. Download and follow the steps as follows:
1. Install and run the software. The home page presents all the options for selecting the data from Windows File System, Public Folder, SharePoint Server, OneDrive for Business, Google Drive. Right-click the SharePoint Server and select Add New SharePoint Site.

2. Provide a Project Name. Input the Site Address, User Name, and Password. Click OK.

3. The wizard will ask if you want to add the SharePoint Server as the destination also. Click No.

4. The SharePoint Site will add as the Source. You can visit all the lists and libraries. The tool will show all the details of it.

5. Now go to destination pane. Right-click SharePoint Server and click Add New SharePoint Site.

6. Provide the Project Name, Site Address, User Name, and Password. Finally, click, OK.

7. The tool will ask if you want to add the SharePoint as Source. Click NO.

8. The SharePoint is present in the destination pane, and now you can conduct the migration.

9. Go to any source list or library and select the data, right-click, and select Copy.

10. Now, go to destination pane. Select the desired library, right-click it, and select Paste.

11. A new wizard shows all the items you have chosen on the source, and you can choose to deselect them. Click Next.

12. The tool shows the Site URL, List/Library/Folder Name, and List/Library/Folder URL. You can use the drop-down and choose any other destination site. Click Next.

13. Select any attribute of the Item and Edit them. Later, click Next to go ahead.

14. The Filter page consists of all the crucial filters for SharePoint tenant to tenant migration. There are Item Copy Options, Date Filter, File Filter, etc. Use these filters and click Next.

15. Set the permissions for data and map the users and role groups. Click Next.

16. There is an exclusive option for scheduling the migration as a suitable period. But you can also choose to run the migration immediately. Click Next.

17. There is a final summary of the whole data which you are migrating. Click Next.

18. A message appears and mentions that the migration will start at the scheduled time. Click Finish.

19. The migration begins (you can click the Stop-Process button and stop the migration).

20. At last, you can get a whole migration report with the status of each migrated item. Click Finish.

Conclusion
It is the best option for SharePoint tenant to tenant migrations, as no feasible manual methods are not available for the same. When you use SharePoint Migration tool, you do not need to struggle with the migration - just add the source and destination and do a copy-&-paste from the source to the destination. There are enough features in the software that make it easier for SharePoint tenant to tenant migration. You have complete control over the migration, and after the migration, you will get a migration report with all the details. That is why this is the most preferred tool for SharePoint tenant to tenant migrations.
Working video - Kernel SharePoint Migrator

This is the best tool for tenant to tenant migrations. When you perform tenant to tenant migrations, then you do not have manual methods. So, use this software and start the migration of data along with complete permissions and metadata.