Tenant level setting to select default for external sharing of the associated site
Currently when a site associated with O365 group is created, external sharing is enabled by default. Microsoft support stated that there no option exists today to toggle this so the sites would be created with external sharing disabled.
There is script that can disable post creation. This is not sufficient since the script would have to be run many many times.
We have SharePoint and OneDrive locked down to prevent external access. O365 Groups circumvents that, and toggling off the external sharing at a group level is not efficient.