Block file shares

AlexCastrojr For external sharing the first option would be an alternative.

Restrict sharing of SharePoint and OneDrive content by domain
https://docs.microsoft.com/en-us/sharepoint/restricted-domains-sharing 

Limit sharing in Microsoft 365
https://docs.microsoft.com/en-us/microsoft-365/solutions/microsoft-365-limit-sharing?view=o365-worldwide 

"While you can use the admin controls described in this article to limit sharing in your organization, we highly recommend that you consider using the security and compliance features available in Microsoft 365 to create a secure sharing environment. See *File collaboration in SharePoint with Microsoft 365 and Teams for highly regulated data for information."

*File collaboration in SharePoint with Microsoft 365
https://docs.microsoft.com/en-us/sharepoint/deploy-file-collaboration