As you may know, you can share content stored on SharePoint Online by getting a link (depending of the settings enabled by your administrator, you may get different options).
Now, SharePoint Online administrators can define which sharing link type (direct, internal or anonymous – again depending of the sharing configuration settings defined) will be the default option.
To change the default sharing link type, log on as with an administrator account on your SharePoint Online Administration portal (https://<your tenant>-admin.sharepoint.com or from the Office 365 admin portal) and reach out the Sharing section
