I'm facing this issue: I'm trying to create an anonymous link to share a document with an user that is external to my organization.
Users with full control/collaboration permissions are able to create link and send it by e-mail. Users with read only are unable to do this. They can create links and share them with users inside the organization, but they are not able to do this with external users (they reicive a message to contact IT dept).
I've enabled all external sharing configurations in the SharePoint admin center. Also enabled using SharePoint Online Shell. There are no limitations relative to specific domains.
Is request a minimun permission level to do this kind of link sharing? Is that documented somewhere?