Change primary sharepoint admin

I did not want the primary owner set to me so using your work around here's how I achieved that:

1. From SPO admin center for the site in question, remove all site admins except myself, the primary admin and the user I want to be the new primary. Be sure to note admins you remove so you can add them back later.
2. Go to the SP site, click COG at top-right > Site Contents > Site Settings > Site Collection Administrators. 
3. Remove everyone (including yourself) except the user you want to be the new Primary Admin and click OK. After it applies you'll see the typical "You need permission to access this site" message, but this is normal.
4. Go back to SPO admin center and refresh the site in question.
5. You should now see that user as the primary admin and can add any additional admins back including yourself.

AB21805 

You need either Global Administrator or SharePoint Administrator role in Microsoft 365 tenant to add and/or remove site admins.

Check: Manage SharePoint site admins 

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