What are your options for old fashioned SharePoint team sites that would benefit from new modern experiences that all hinge on an Office 365 group, like Teams for example? One very simple option is to Group-ify and Team-ify the classic team site....
;tl;dr A recent attempt to share a site collection provisioned by the new "Create Site" link in SharePoint Online revealed that in order to share the site collection with external users you must change the sites "SharingPolicy" property from the default ExistingExternalUserSharingOnly to ExternalUserSharingOnly to enable new external user invitations. This must be done with the Set-SPOSite PowerShell Cmdlet [https://technet.microsoft.com/en-us/library/fp161394.aspx] The Back Story I recently ha...