Service Restored:
Office 365 distribution groups can now be managed by the group owners directly.

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Previous Description (April 28, 2023 09:13):

If you are an owner who requires changes to the membership of a Distribution Group, please submit an IT Services Help ticket with details concerning the Group name and the email addresses of those who you wish to have added or removed from the Group.

For changes to an Owner, the request for a Group Owner change will need to be requested via the Calendar Resources, Shared Mailboxes, Distribution Lists Catalog Item by an IT Admin Rep.

IT Service will make the necessary change for you while Group Management continues to be broken for Group owners in Office 365.

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Previous Description (April 27, 2023 10:41):

Microsoft have confirmed a problem exists currently with managing distribution groups..
Some users have also reported issues in viewing distribution groups in which they are members.

This notification will be updated as more information becomes available.