A Microsoft 365 Group and connected Microsoft Teams team can become ownerless when the last owner’s account is deleted or disabled in the Azure Active Directory. New members cannot be invited or approved, if the group is private, team settings cannot be changed, and shared channels cannot be added – a lot of things are missing when there is no owner on the team. And if previous owners have limited members’ functionality or enabled moderation, things are even worse. The first tactic for preventing ownerless groups/teams is to have at least two owners, this should be mandatory and one of the responsibilities of team owners.
With the new Ownerless Group Policy, it is possible to request most active team members be promoted to team owners. The Ownerless Group Policy can be activated and configured on Microsoft 365 Admin portal in Microsoft 365 Group settings.

By default Sender is the account which enabled the policy, notifications are sent weekly for four weeks to the five most active members, and all active members can promote themselves as the owner of the team.
Configuring a custom policy
With a custom policy, administrators can control which members are receiving the request, the sender, subject, and content of the email message, and is the policy targeted to all or just specific Microsoft 365 Groups.
On Notification options, administrators can define which members’ requests are sent. Admins can allow or block certain members from receiving notifications based on group membership, or just include all members. The number of active members for notifications can be also defined with a maximum of 90. Guests are not included. And the last option is to configure how many weeks notification emails are sent with a maximum of seven weeks.

The email sender can be a user or a Microsoft 365 Group.

With subject and message settings, administrators can configure personalized email. The group name can be added with $Group.Name tag and personal greeting with user’s name with $User.DisplayName tag. Actionable buttons are added automatically.

And the last setting is to select is the policy targeted to all Microsoft 365 Groups or just specific groups.

How does it work then?
Flow is simple. Active members receive an email from the defined sender.

Once a member clicks Yes, she will be promoted to the group owner. All members who received the same email can be promoted.
More information on Microsoft Learn
- Manage ownerless Microsoft 365 groups and teams: https://learn.microsoft.com/en-us/microsoft-365/admin/create-groups/ownerless-groups-teams
- FAQ: https://learn.microsoft.com/en-us/exchange/troubleshoot/groups-and-distribution-lists/ownerless-group-policy