How to add owner

yanliangcapgeminico As you don't have tenant administrator permissions, you have to connect with your IT team or M365 tenant administrator/Groups administrator (if you know the person).

You can request them to add you as an owner of the Microsoft teams "team" (associated M365 group).

Documentations:

1. Add or remove members from Microsoft 365 groups using the admin center 
2. Assign a new owner to an orphaned group 

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Hi yanliangcapgeminico,

you need to be an M365 admin to do this. (As you are taking over ownership of a team)
If you don't have access to the admin center you should contact your IT department and open a ticket.

There is one other choce if your company did setup the "Microsoft 365 ownerless group policy" (https://learn.microsoft.com/en-us/exchange/troubleshoot/groups-and-distribution-lists/ownerless-group-policy ).
In that case the most active users in that team got an email  with an actionable button that asked them to take over the ownerless team.
But if you or other team members did not get this email then you'll have to contact an admin.

Best Regards,
Sven