We had lost some distribution groups recently. It would be nice to have a warning or a workaround to not overwrite cloud-only list when an on-prem user or group matches the one on Office 365/Azure AD. Some of our OU was supposed to be filtered when we worked with a Microsoft engineer.
Since our up-to-date distribution lists got overwritten by older lists from our on-prem AD and Microsoft does not back up groups on the cloud, we had to create all our lost distribution list from scratch.