Posting links from other people’s websites
It will no longer be possible to customize the image, title or description of a link preview in a Page post. When sharing links to other people’s websites, Facebook will pull link previews from the website’s metadata. If this metadata is not available, a complete link preview with an image may not be generated.
See Facebook’s documentation to ensure that your own website is set up to generate optimal link previews.
Page posts scheduled to publish after December 18 will do so without any link customizations. The links will instead display their default metadata, if available.
See View, edit, or delete scheduled content to edit your scheduled messages.
Posting links from your own domains
Facebook has enabled a tool in the Facebook Business Manager to let businesses continue customizing Page post previews for links to their own domains. It’s called Domain Verification.
Hootsuite’s Composer supports link preview customization for verified domains. See this article for more details on the steps required to continue customizing your Page post link previews.