Office 365 Groups will now have unique mailNickname

TonyRedmondOK, thanks for the tip about the Group Identifier on the Site object of a Group.. I checked but this identifier is an empty guid (for all Groups, tested on multiple tenants) as it seems (I use version '16.0.9119.1200' of the 'Microsoft.Online.SharePoint.PowerShell' module btw)

RelatedGroupId                              : 00000000-0000-0000-0000-000000000000
GroupId                                     : 00000000-0000-0000-0000-000000000000

We create Groups/Teams by using SPO CSOM from PnP, and the Alias is always used in this process. like so: https://docs.microsoft.com/en-us/sharepoint/dev/solution-guidance/modern-experience-customizations-provisioning-sites#provisioning-modern-team-sites

We have to do it like this because all other Team/Group creation endpoints do not create the SharePoint Site immediately, and we need some basic things configured in the Site as soon as the Group gets created.

We also set Azure AD settings/policies, Exchange Online settings/policies, Teams settings/policies and Compliance retention policies by using the object model during this provisioning process (using the Alias as an identifier)

After this has all been set, at a certain point in time (could be a day, or more) the Alias changes by backend processes to a guid, I have no idea why and how this is triggered (Maybe something with the Compliance Center Object Model that is triggering this after a certain time, perhaps when actually creation the Preservation Hold Library?). If you could find out I would appreciate it very much.

BTW. I just renamed the aliases all back to the ones I defined myself by using powershell (Set-UnifiedGroup [guid] -Alias [myownalias]), but I expect I will have to check for alias changes and repeat this for the time being. (Get-UnifiedGroup | select DisplayName,Alias).

Thanks for your continued assistance!