There is Azure AD Connect in use to synchronize the environment and also an Exchange 2010 server on-premise.
Our users are also synchronized locally and have a mailbox in Exchange Online.
If group membership can only be managed in the local Active Directory, how can I enable users to add themselves to groups that have the status "Open"?
Is it possible to provide an existing, synchronized distribution group with a self-service so that the users can decide for themselves whether to join or leave?
According to the article below, the self-service function is not available for distribution lists.
Can the synchronized distribution list be updated to a Microsoft 365 group to enable self-service (Azure AD Premium Plan 1 required)?
Is there another way to activate the existing distribution list for membership approvals, e.g. with attribute extension?