Securing shared Google drives with Google trusted domains

If you need to share files on your Google drives with users that are external to your organization and they use Google accounts as well, a more security-minded option is to use use a list domains that are trusted and only let your users share with those trusted domains.

From the Google Admin console navigate to:

Account > Domains > Allowlisted domains > Add domain

From here you simply add the list of other domains you would like to trust. Be sure to carefully review and turn off any file sharing rules for Google Drive or other Google services that allow sharing to anybody outside your organization unless they are a trusted domain.