You can have multiple owners for an Azure Active Directory security group so if you want to replace an owner, you just need to add a new owner and then remove the previous owner. The account that you want to make an owner much already be a member of the group.
Log into the Azure Portal with the Administrator account and then open Active Directory.
Select Groups and then click on the group that you want to change the owner for.
In the menu list to the left of the group overview, click on Owners.
Click on Add owners, which will open an overlay panel.
In the Add Owners panel, search for and then select the user account that you want to promote. Click on the Select button.
Refresh the main group page.
Click on Owners again. In the Owners screen, click on the owner that you want to remove. Click on the Remove button at the top of the screen.
Confirm the removal by clicking Yes in the popup dialog box.